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Posted to commits@hivemall.apache.org by my...@apache.org on 2017/09/13 14:10:28 UTC
[16/23] incubator-hivemall-site git commit: Updated userguide for
evaluation section
http://git-wip-us.apache.org/repos/asf/incubator-hivemall-site/blob/a98b42f8/userguide/eval/rank.html
----------------------------------------------------------------------
diff --git a/userguide/eval/rank.html b/userguide/eval/rank.html
index 879fda1..7b20e57 100644
--- a/userguide/eval/rank.html
+++ b/userguide/eval/rank.html
@@ -100,7 +100,7 @@
<link rel="next" href="datagen.html" />
- <link rel="prev" href="auc.html" />
+ <link rel="prev" href="regression.html" />
</head>
@@ -244,7 +244,7 @@
<b>1.3.1.</b>
- Explicit addBias() for better prediction
+ Explicit add_bias() for better prediction
</a>
@@ -707,14 +707,14 @@
- <li class="chapter " data-level="4.1" data-path="stat_eval.html">
+ <li class="chapter " data-level="4.1" data-path="binary_classification_measures.html">
- <a href="stat_eval.html">
+ <a href="binary_classification_measures.html">
<b>4.1.</b>
- Statistical evaluation of a prediction model
+ Binary Classification Metrics
</a>
@@ -743,13 +743,43 @@
</li>
- <li class="chapter active" data-level="4.2" data-path="rank.html">
+ <li class="chapter " data-level="4.2" data-path="multilabel_classification_measures.html">
- <a href="rank.html">
+ <a href="multilabel_classification_measures.html">
<b>4.2.</b>
+ Multi-label Classification Metrics
+
+ </a>
+
+
+
+ </li>
+
+ <li class="chapter " data-level="4.3" data-path="regression.html">
+
+ <a href="regression.html">
+
+
+ <b>4.3.</b>
+
+ Regression metrics
+
+ </a>
+
+
+
+ </li>
+
+ <li class="chapter active" data-level="4.4" data-path="rank.html">
+
+ <a href="rank.html">
+
+
+ <b>4.4.</b>
+
Ranking Measures
</a>
@@ -758,12 +788,12 @@
</li>
- <li class="chapter " data-level="4.3" data-path="datagen.html">
+ <li class="chapter " data-level="4.5" data-path="datagen.html">
<a href="datagen.html">
- <b>4.3.</b>
+ <b>4.5.</b>
Data Generation
@@ -774,12 +804,12 @@
<ul class="articles">
- <li class="chapter " data-level="4.3.1" data-path="lr_datagen.html">
+ <li class="chapter " data-level="4.5.1" data-path="lr_datagen.html">
<a href="lr_datagen.html">
- <b>4.3.1.</b>
+ <b>4.5.1.</b>
Logistic Regression data generation
@@ -2179,6 +2209,7 @@
<li><a href="../recommend/item_based_cf.html">Recommendation based on item-based collaborative filtering</a></li>
</ul>
<p>This page focuses on evaluation of the results from such ranking problems.</p>
+<div class="panel panel-warning"><div class="panel-heading"><h3 class="panel-title" id="caution"><i class="fa fa-exclamation-triangle"></i> Caution</h3></div><div class="panel-body"><p>In order to obtain ranked list of items, this page introduces queries using <code>to_ordered_map()</code> such as <code>map_values(to_ordered_map(score, itemid, true))</code>. However, this kind of usage has a potential issue that multiple <code>itemid</code>-s (i.e., values) which have the exactly same <code>score</code> (i.e., key) will be aggregated to single arbitrary <code>itemid</code>, because <code>to_ordered_map()</code> creates a key-value map which uses duplicated <code>score</code> as key.</p><p>Hence, if map key could duplicate on more then one map values, we recommend you to use <code>to_ordered_list(value, key, '-reverse')</code> instead of <code>map_values(to_ordered_map(key, value, true))</code>. The alternative approach is available from Hivemall v0.5-rc.1 or later.</p></di
v></div>
<h1 id="binary-response-measures">Binary Response Measures</h1>
<p>In a context of ranking problem, <strong>binary response</strong> means that binary labels are assigned to items, and positive items are considered as <em>truth</em> observations.</p>
<p>In a <code>dummy_truth</code> table, we assume that there are three users (<code>userid = 1, 2, 3</code>) who have exactly same three truth ranked items (<code>itemid = 1, 2, 4</code>) chosen from existing six items:</p>
@@ -2301,7 +2332,7 @@
</tbody>
</table>
<p>How can we compare <code>dummy_rec</code> with <code>dummy_truth</code> to figure out the accuracy of <code>dummy_rec</code>?</p>
-<p>To be more precise, in case we built a recommender system, let a target user <span class="katex"><span class="katex-mathml"><math><semantics><mrow><mi>u</mi><mo>∈</mo><mrow><mi mathvariant="script">U</mi></mrow></mrow><annotation encoding="application/x-tex">u \in \mathcal{U}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.68333em;"></span><span class="strut bottom" style="height:0.72243em;vertical-align:-0.0391em;"></span><span class="base textstyle uncramped"><span class="mord mathit">u</span><span class="mrel">∈</span><span class="mord textstyle uncramped"><span class="mord mathcal" style="margin-right:0.09931em;">U</span></span></span></span></span>, set of all items <span class="katex"><span class="katex-mathml"><math><semantics><mrow><mrow><mi mathvariant="script">I</mi></mrow></mrow><annotation encoding="application/x-tex">\mathcal{I}</annotation></semantics></math></span><span class="katex
-html" aria-hidden="true"><span class="strut" style="height:0.68333em;"></span><span class="strut bottom" style="height:0.68333em;vertical-align:0em;"></span><span class="base textstyle uncramped"><span class="mord textstyle uncramped"><span class="mord mathcal" style="margin-right:0.07382em;">I</span></span></span></span></span>, ordered set of top-k recommended items <span class="katex"><span class="katex-mathml"><math><semantics><mrow><msub><mi>I</mi><mi>k</mi></msub><mo>(</mo><mi>u</mi><mo>)</mo><mo>⊂</mo><mrow><mi mathvariant="script">I</mi></mrow></mrow><annotation encoding="application/x-tex">I_k(u) \subset \mathcal{I}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.75em;"></span><span class="strut bottom" style="height:1em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class="mord"><span class="mord mathit" style="margin-right:0.07847em;">I</span><span class="vlist"><sp
an style="top:0.15em;margin-right:0.05em;margin-left:-0.07847em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped"><span class="mord mathit" style="margin-right:0.03148em;">k</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span><span class="mopen">(</span><span class="mord mathit">u</span><span class="mclose">)</span><span class="mrel">⊂</span><span class="mord textstyle uncramped"><span class="mord mathcal" style="margin-right:0.07382em;">I</span></span></span></span></span>, and set of truth items <span class="katex"><span class="katex-mathml"><math><semantics><mrow><msubsup><mrow><mi mathvariant="script">I</mi></mrow><mi>u</mi><mo>+</mo></msubsup></mrow><annotation encoding="application/x-tex">\mathcal{I}^+_u</annotation></semantics></math></span><span
class="katex-html" aria-hidden="true"><span class="strut" style="height:0.771331em;"></span><span class="strut bottom" style="height:1.0183309999999999em;vertical-align:-0.247em;"></span><span class="base textstyle uncramped"><span class=""><span class="mord textstyle uncramped"><span class="mord mathcal" style="margin-right:0.07382em;">I</span></span><span class="vlist"><span style="top:0.247em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped"><span class="mord mathit">u</span></span></span><span style="top:-0.363em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle uncramped"><span class="mord">+</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</
span></span></span></span></span></span>. Hence, when we launch top-2 recommendation for the above tables, <span class="katex"><span class="katex-mathml"><math><semantics><mrow><mrow><mi mathvariant="script">U</mi></mrow><mo>=</mo><mo>{</mo><mn>1</mn><mo separator="true">,</mo><mn>2</mn><mo separator="true">,</mo><mn>3</mn><mo>}</mo></mrow><annotation encoding="application/x-tex">\mathcal{U} = \{1, 2, 3\}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.75em;"></span><span class="strut bottom" style="height:1em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class="mord textstyle uncramped"><span class="mord mathcal" style="margin-right:0.09931em;">U</span></span><span class="mrel">=</span><span class="mopen">{</span><span class="mord mathrm">1</span><span class="mpunct">,</span><span class="mord mathrm">2</span><span class="mpunct">,</span><span class="mord mathrm">3</span><span class=
"mclose">}</span></span></span></span>, <span class="katex"><span class="katex-mathml"><math><semantics><mrow><mrow><mi mathvariant="script">I</mi></mrow><mo>=</mo><mo>{</mo><mn>1</mn><mo separator="true">,</mo><mn>2</mn><mo separator="true">,</mo><mn>3</mn><mo separator="true">,</mo><mn>4</mn><mo separator="true">,</mo><mn>5</mn><mo separator="true">,</mo><mn>6</mn><mo>}</mo></mrow><annotation encoding="application/x-tex">\mathcal{I} = \{1, 2, 3, 4, 5, 6\}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.75em;"></span><span class="strut bottom" style="height:1em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class="mord textstyle uncramped"><span class="mord mathcal" style="margin-right:0.07382em;">I</span></span><span class="mrel">=</span><span class="mopen">{</span><span class="mord mathrm">1</span><span class="mpunct">,</span><span class="mord mathrm">2</span><span class="mpunct">,
</span><span class="mord mathrm">3</span><span class="mpunct">,</span><span class="mord mathrm">4</span><span class="mpunct">,</span><span class="mord mathrm">5</span><span class="mpunct">,</span><span class="mord mathrm">6</span><span class="mclose">}</span></span></span></span> and <span class="katex"><span class="katex-mathml"><math><semantics><mrow><msub><mi>I</mi><mn>2</mn></msub><mo>(</mo><mi>u</mi><mo>)</mo><mo>=</mo><mo>{</mo><mn>1</mn><mo separator="true">,</mo><mn>3</mn><mo>}</mo></mrow><annotation encoding="application/x-tex">I_2(u) = \{1, 3\}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.75em;"></span><span class="strut bottom" style="height:1em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class="mord"><span class="mord mathit" style="margin-right:0.07847em;">I</span><span class="vlist"><span style="top:0.15em;margin-right:0.05em;margin-left:-0.07847em;"><span class="f
ontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped"><span class="mord mathrm">2</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span><span class="mopen">(</span><span class="mord mathit">u</span><span class="mclose">)</span><span class="mrel">=</span><span class="mopen">{</span><span class="mord mathrm">1</span><span class="mpunct">,</span><span class="mord mathrm">3</span><span class="mclose">}</span></span></span></span> which consists of two highest-scored items, and <span class="katex"><span class="katex-mathml"><math><semantics><mrow><msubsup><mrow><mi mathvariant="script">I</mi></mrow><mi>u</mi><mo>+</mo></msubsup><mo>=</mo><mo>{</mo><mn>1</mn><mo separator="true">,</mo><mn>2</mn><mo separator="true">,</mo><mn>4</mn><mo>}</mo></mrow><annotation encoding="application/x-tex">
\mathcal{I}^+_u = \{1, 2, 4\}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.771331em;"></span><span class="strut bottom" style="height:1.021331em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class=""><span class="mord textstyle uncramped"><span class="mord mathcal" style="margin-right:0.07382em;">I</span></span><span class="vlist"><span style="top:0.247em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped"><span class="mord mathit">u</span></span></span><span style="top:-0.363em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle uncramped"><span class="mord">+</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5
"><span style="font-size:0em;">​</span></span>​</span></span></span><span class="mrel">=</span><span class="mopen">{</span><span class="mord mathrm">1</span><span class="mpunct">,</span><span class="mord mathrm">2</span><span class="mpunct">,</span><span class="mord mathrm">4</span><span class="mclose">}</span></span></span></span>.</p>
+<p>To be more precise, in case we built a recommender system, let a target user <span class="katex"><span class="katex-mathml"><math><semantics><mrow><mi>u</mi><mo>∈</mo><mrow><mi mathvariant="script">U</mi></mrow></mrow><annotation encoding="application/x-tex">u \in \mathcal{U}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.68333em;"></span><span class="strut bottom" style="height:0.72243em;vertical-align:-0.0391em;"></span><span class="base textstyle uncramped"><span class="mord mathit">u</span><span class="mrel">∈</span><span class="mord textstyle uncramped"><span class="mord mathcal" style="margin-right:0.09931em;">U</span></span></span></span></span>, set of all items <span class="katex"><span class="katex-mathml"><math><semantics><mrow><mrow><mi mathvariant="script">I</mi></mrow></mrow><annotation encoding="application/x-tex">\mathcal{I}</annotation></semantics></math></span><span class="katex
-html" aria-hidden="true"><span class="strut" style="height:0.68333em;"></span><span class="strut bottom" style="height:0.68333em;vertical-align:0em;"></span><span class="base textstyle uncramped"><span class="mord textstyle uncramped"><span class="mord mathcal" style="margin-right:0.07382em;">I</span></span></span></span></span>, ordered set of top-k recommended items <span class="katex"><span class="katex-mathml"><math><semantics><mrow><msub><mi>I</mi><mi>k</mi></msub><mo>(</mo><mi>u</mi><mo>)</mo><mo>⊂</mo><mrow><mi mathvariant="script">I</mi></mrow></mrow><annotation encoding="application/x-tex">I_k(u) \subset \mathcal{I}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.75em;"></span><span class="strut bottom" style="height:1em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class="mord"><span class="mord mathit" style="margin-right:0.07847em;">I</span><span class="msupsub"><
span class="vlist"><span style="top:0.15em;margin-right:0.05em;margin-left:-0.07847em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped mtight"><span class="mord mathit mtight" style="margin-right:0.03148em;">k</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span></span><span class="mopen">(</span><span class="mord mathit">u</span><span class="mclose">)</span><span class="mrel">⊂</span><span class="mord textstyle uncramped"><span class="mord mathcal" style="margin-right:0.07382em;">I</span></span></span></span></span>, and set of truth items <span class="katex"><span class="katex-mathml"><math><semantics><mrow><msubsup><mrow><mi mathvariant="script">I</mi></mrow><mi>u</mi><mo>+</mo></msubsup></mrow><annotation encoding="application/x-tex">\mathcal{I}^+_u</
annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.771331em;"></span><span class="strut bottom" style="height:1.0183309999999999em;vertical-align:-0.247em;"></span><span class="base textstyle uncramped"><span class="mord"><span class="mord textstyle uncramped"><span class="mord mathcal" style="margin-right:0.07382em;">I</span></span><span class="msupsub"><span class="vlist"><span style="top:0.247em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped mtight"><span class="mord mathit mtight">u</span></span></span><span style="top:-0.363em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle uncramped mtight"><span class="mbin mtight">+</span></span></span><span class="baseline-fix"><span class="
fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span></span></span></span></span>. Hence, when we launch top-2 recommendation for the above tables, <span class="katex"><span class="katex-mathml"><math><semantics><mrow><mrow><mi mathvariant="script">U</mi></mrow><mo>=</mo><mo>{</mo><mn>1</mn><mo separator="true">,</mo><mn>2</mn><mo separator="true">,</mo><mn>3</mn><mo>}</mo></mrow><annotation encoding="application/x-tex">\mathcal{U} = \{1, 2, 3\}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.75em;"></span><span class="strut bottom" style="height:1em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class="mord textstyle uncramped"><span class="mord mathcal" style="margin-right:0.09931em;">U</span></span><span class="mrel">=</span><span class="mopen">{</span><span class="mord mathrm">1</span><span class="mpunct">,</span><span
class="mord mathrm">2</span><span class="mpunct">,</span><span class="mord mathrm">3</span><span class="mclose">}</span></span></span></span>, <span class="katex"><span class="katex-mathml"><math><semantics><mrow><mrow><mi mathvariant="script">I</mi></mrow><mo>=</mo><mo>{</mo><mn>1</mn><mo separator="true">,</mo><mn>2</mn><mo separator="true">,</mo><mn>3</mn><mo separator="true">,</mo><mn>4</mn><mo separator="true">,</mo><mn>5</mn><mo separator="true">,</mo><mn>6</mn><mo>}</mo></mrow><annotation encoding="application/x-tex">\mathcal{I} = \{1, 2, 3, 4, 5, 6\}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.75em;"></span><span class="strut bottom" style="height:1em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class="mord textstyle uncramped"><span class="mord mathcal" style="margin-right:0.07382em;">I</span></span><span class="mrel">=</span><span class="mopen">{</span><span class="mo
rd mathrm">1</span><span class="mpunct">,</span><span class="mord mathrm">2</span><span class="mpunct">,</span><span class="mord mathrm">3</span><span class="mpunct">,</span><span class="mord mathrm">4</span><span class="mpunct">,</span><span class="mord mathrm">5</span><span class="mpunct">,</span><span class="mord mathrm">6</span><span class="mclose">}</span></span></span></span> and <span class="katex"><span class="katex-mathml"><math><semantics><mrow><msub><mi>I</mi><mn>2</mn></msub><mo>(</mo><mi>u</mi><mo>)</mo><mo>=</mo><mo>{</mo><mn>1</mn><mo separator="true">,</mo><mn>3</mn><mo>}</mo></mrow><annotation encoding="application/x-tex">I_2(u) = \{1, 3\}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.75em;"></span><span class="strut bottom" style="height:1em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class="mord"><span class="mord mathit" style="margin-right:0.07847em;">I</span
><span class="msupsub"><span class="vlist"><span style="top:0.15em;margin-right:0.05em;margin-left:-0.07847em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped mtight"><span class="mord mathrm mtight">2</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span></span><span class="mopen">(</span><span class="mord mathit">u</span><span class="mclose">)</span><span class="mrel">=</span><span class="mopen">{</span><span class="mord mathrm">1</span><span class="mpunct">,</span><span class="mord mathrm">3</span><span class="mclose">}</span></span></span></span> which consists of two highest-scored items, and <span class="katex"><span class="katex-mathml"><math><semantics><mrow><msubsup><mrow><mi mathvariant="script">I</mi></mrow><mi>u</mi><mo>+</mo></msubsup><mo>=</mo><mo>{
</mo><mn>1</mn><mo separator="true">,</mo><mn>2</mn><mo separator="true">,</mo><mn>4</mn><mo>}</mo></mrow><annotation encoding="application/x-tex">\mathcal{I}^+_u = \{1, 2, 4\}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.771331em;"></span><span class="strut bottom" style="height:1.021331em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class="mord"><span class="mord textstyle uncramped"><span class="mord mathcal" style="margin-right:0.07382em;">I</span></span><span class="msupsub"><span class="vlist"><span style="top:0.247em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped mtight"><span class="mord mathit mtight">u</span></span></span><span style="top:-0.363em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">&#
x200B;</span></span><span class="reset-textstyle scriptstyle uncramped mtight"><span class="mbin mtight">+</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span></span><span class="mrel">=</span><span class="mopen">{</span><span class="mord mathrm">1</span><span class="mpunct">,</span><span class="mord mathrm">2</span><span class="mpunct">,</span><span class="mord mathrm">4</span><span class="mclose">}</span></span></span></span>.</p>
<p>Evaluation of the ordered sets can be done by the following query:</p>
<pre><code class="lang-sql">with truth as (
<span class="hljs-keyword">select</span> userid, collect_set(itemid) <span class="hljs-keyword">as</span> truth
@@ -2320,12 +2351,12 @@ rec <span class="hljs-keyword">as</span> (
<span class="hljs-comment">-- rec = [1,3,2,6], truth = [1,2,4] for each user</span>
<span class="hljs-comment">-- Recall@k</span>
- recall(t1.rec, t2.truth, t1.max_k) <span class="hljs-keyword">as</span> recall,
- recall(t1.rec, t2.truth, <span class="hljs-number">2</span>) <span class="hljs-keyword">as</span> recall_at_2,
+ recall_at(t1.rec, t2.truth, t1.max_k) <span class="hljs-keyword">as</span> recall,
+ recall_at(t1.rec, t2.truth, <span class="hljs-number">2</span>) <span class="hljs-keyword">as</span> recall_at_2,
<span class="hljs-comment">-- Precision@k</span>
- <span class="hljs-keyword">precision</span>(t1.rec, t2.truth, t1.max_k) <span class="hljs-keyword">as</span> <span class="hljs-keyword">precision</span>,
- <span class="hljs-keyword">precision</span>(t1.rec, t2.truth, <span class="hljs-number">2</span>) <span class="hljs-keyword">as</span> precision_at_2,
+ precision_at(t1.rec, t2.truth, t1.max_k) <span class="hljs-keyword">as</span> <span class="hljs-keyword">precision</span>,
+ precision_at(t1.rec, t2.truth, <span class="hljs-number">2</span>) <span class="hljs-keyword">as</span> precision_at_2,
<span class="hljs-comment">-- MAP</span>
average_precision(t1.rec, t2.truth, t1.max_k) <span class="hljs-keyword">as</span> average_precision,
@@ -2389,47 +2420,48 @@ rec <span class="hljs-keyword">as</span> (
</tbody>
</table>
<p>Here, we introduce the six measures for evaluation of ranked list of items. Importantly, each metric has a different concept behind formulation, and the accuracy measured by the metrics shows different values even for the exactly same input as demonstrated above. Thus, evaluation using multiple ranking measures is more convincing, and it should be easy in Hivemall.</p>
+<div class="panel panel-warning"><div class="panel-heading"><h3 class="panel-title" id="caution"><i class="fa fa-exclamation-triangle"></i> Caution</h3></div><div class="panel-body"><p>Before Hivemall v0.5-rc.1, <code>recall_at()</code> and <code>precision_at()</code> are respectively registered as <code>recall()</code> and <code>precision()</code>. However, since <code>precision</code> is a reserved keyword from Hive v2.2.0, <a href="https://issues.apache.org/jira/browse/HIVEMALL-140" target="_blank">we renamed the function names</a>. If you are still using <code>recall()</code> and/or <code>precision()</code>, we strongly recommend you to use the latest version of Hivemall and replace them with the newer function names.</p></div></div>
<h2 id="recall-at-k">Recall-At-k</h2>
<p><strong>Recall-at-k (Recall@k)</strong> indicates coverage of truth samples as a result of top-k recommendation. The value is computed by the following equation:
<span class="katex-display"><span class="katex"><span class="katex-mathml"><math><semantics><mrow><mrow><mi mathvariant="normal">R</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">c</mi><mi mathvariant="normal">a</mi><mi mathvariant="normal">l</mi><mi mathvariant="normal">l</mi><mi mathvariant="normal">@</mi></mrow><mi>k</mi><mo>=</mo><mfrac><mrow><mi mathvariant="normal">∣</mi><msubsup><mrow><mi mathvariant="script">I</mi></mrow><mi>u</mi><mo>+</mo></msubsup><mo>∩</mo><msub><mi>I</mi><mi>k</mi></msub><mo>(</mo><mi>u</mi><mo>)</mo><mi mathvariant="normal">∣</mi></mrow><mrow><mi mathvariant="normal">∣</mi><msubsup><mrow><mi mathvariant="script">I</mi></mrow><mi>u</mi><mo>+</mo></msubsup><mi mathvariant="normal">∣</mi></mrow></mfrac><mi mathvariant="normal">.</mi></mrow><annotation encoding="application/x-tex">
\mathrm{Recall@}k = \frac{|\mathcal{I}^+_u \cap I_k(u)|}{|\mathcal{I}^+_u|}.
-</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:1.448331em;"></span><span class="strut bottom" style="height:2.384331em;vertical-align:-0.936em;"></span><span class="base displaystyle textstyle uncramped"><span class="mord displaystyle textstyle uncramped"><span class="mord mathrm">R</span><span class="mord mathrm">e</span><span class="mord mathrm">c</span><span class="mord mathrm">a</span><span class="mord mathrm">l</span><span class="mord mathrm">l</span><span class="mord mathrm">@</span></span><span class="mord mathit" style="margin-right:0.03148em;">k</span><span class="mrel">=</span><span class="mord reset-textstyle displaystyle textstyle uncramped"><span class="sizing reset-size5 size5 reset-textstyle textstyle uncramped nulldelimiter"></span><span class="mfrac"><span class="vlist"><span style="top:0.686em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><s
pan class="reset-textstyle textstyle cramped"><span class="mord textstyle cramped"><span class="mord mathrm">∣</span><span class=""><span class="mord textstyle cramped"><span class="mord mathcal" style="margin-right:0.07382em;">I</span></span><span class="vlist"><span style="top:0.247em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped"><span class="mord mathit">u</span></span></span><span style="top:-0.29733em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped"><span class="mord">+</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span><span class="mord mathrm">∣</span></span></span></span><span style="top:-0.230
0000000000001em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle textstyle uncramped frac-line"></span></span><span style="top:-0.677em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle textstyle uncramped"><span class="mord textstyle uncramped"><span class="mord mathrm">∣</span><span class=""><span class="mord textstyle uncramped"><span class="mord mathcal" style="margin-right:0.07382em;">I</span></span><span class="vlist"><span style="top:0.247em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped"><span class="mord mathit">u</span></span></span><span style="top:-0.363em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span
class="reset-textstyle scriptstyle uncramped"><span class="mord">+</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span><span class="mbin">∩</span><span class="mord"><span class="mord mathit" style="margin-right:0.07847em;">I</span><span class="vlist"><span style="top:0.15em;margin-right:0.05em;margin-left:-0.07847em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped"><span class="mord mathit" style="margin-right:0.03148em;">k</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span><span class="mopen">(</span><span class="mord mathit">u</span><span class="mclose">)</span><span class="mord mathrm">∣</span></span></span></span><span c
lass="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span><span class="sizing reset-size5 size5 reset-textstyle textstyle uncramped nulldelimiter"></span></span><span class="mord mathrm">.</span></span></span></span></span>
-Here, <span class="katex"><span class="katex-mathml"><math><semantics><mrow><mi mathvariant="normal">∣</mi><msubsup><mrow><mi mathvariant="script">I</mi></mrow><mi>u</mi><mo>+</mo></msubsup><mo>∩</mo><msub><mi>I</mi><mi>k</mi></msub><mo>(</mo><mi>u</mi><mo>)</mo><mi mathvariant="normal">∣</mi></mrow><annotation encoding="application/x-tex">|\mathcal{I}^+_u \cap I_k(u)|</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.771331em;"></span><span class="strut bottom" style="height:1.021331em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class="mord mathrm">∣</span><span class=""><span class="mord textstyle uncramped"><span class="mord mathcal" style="margin-right:0.07382em;">I</span></span><span class="vlist"><span style="top:0.247em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span cla
ss="reset-textstyle scriptstyle cramped"><span class="mord mathit">u</span></span></span><span style="top:-0.363em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle uncramped"><span class="mord">+</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span><span class="mbin">∩</span><span class="mord"><span class="mord mathit" style="margin-right:0.07847em;">I</span><span class="vlist"><span style="top:0.15em;margin-right:0.05em;margin-left:-0.07847em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped"><span class="mord mathit" style="margin-right:0.03148em;">k</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size
5"><span style="font-size:0em;">​</span></span>​</span></span></span><span class="mopen">(</span><span class="mord mathit">u</span><span class="mclose">)</span><span class="mord mathrm">∣</span></span></span></span> is the number of true positives. If <span class="katex"><span class="katex-mathml"><math><semantics><mrow><msub><mi>I</mi><mn>2</mn></msub><mo>(</mo><mi>u</mi><mo>)</mo><mo>=</mo><mo>{</mo><mn>1</mn><mo separator="true">,</mo><mn>3</mn><mo>}</mo></mrow><annotation encoding="application/x-tex">I_2(u) = \{1, 3\}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.75em;"></span><span class="strut bottom" style="height:1em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class="mord"><span class="mord mathit" style="margin-right:0.07847em;">I</span><span class="vlist"><span style="top:0.15em;margin-right:0.05em;margin-left:-0.07847em;"><span class="fontsize-ensu
rer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped"><span class="mord mathrm">2</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span><span class="mopen">(</span><span class="mord mathit">u</span><span class="mclose">)</span><span class="mrel">=</span><span class="mopen">{</span><span class="mord mathrm">1</span><span class="mpunct">,</span><span class="mord mathrm">3</span><span class="mclose">}</span></span></span></span> and <span class="katex"><span class="katex-mathml"><math><semantics><mrow><msubsup><mrow><mi mathvariant="script">I</mi></mrow><mi>u</mi><mo>+</mo></msubsup><mo>=</mo><mo>{</mo><mn>1</mn><mo separator="true">,</mo><mn>2</mn><mo separator="true">,</mo><mn>4</mn><mo>}</mo></mrow><annotation encoding="application/x-tex">\mathcal{I}^+_u = \{1, 2, 4\}</annotation></semantics></
math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.771331em;"></span><span class="strut bottom" style="height:1.021331em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class=""><span class="mord textstyle uncramped"><span class="mord mathcal" style="margin-right:0.07382em;">I</span></span><span class="vlist"><span style="top:0.247em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped"><span class="mord mathit">u</span></span></span><span style="top:-0.363em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle uncramped"><span class="mord">+</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>&#x
200B;</span></span></span><span class="mrel">=</span><span class="mopen">{</span><span class="mord mathrm">1</span><span class="mpunct">,</span><span class="mord mathrm">2</span><span class="mpunct">,</span><span class="mord mathrm">4</span><span class="mclose">}</span></span></span></span>, <span class="katex"><span class="katex-mathml"><math><semantics><mrow><mrow><mi mathvariant="normal">R</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">c</mi><mi mathvariant="normal">a</mi><mi mathvariant="normal">l</mi><mi mathvariant="normal">l</mi><mi mathvariant="normal">@</mi></mrow><mn>2</mn><mo>=</mo><mn>1</mn><mi mathvariant="normal">/</mi><mn>3</mn><mo>≈</mo><mn>0</mn><mi mathvariant="normal">.</mi><mn>3</mn><mn>3</mn><mn>3</mn></mrow><annotation encoding="application/x-tex">\mathrm{Recall@}2 = 1 / 3 \approx 0.333</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.75em;"></span><span class="strut bottom
" style="height:1em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class="mord textstyle uncramped"><span class="mord mathrm">R</span><span class="mord mathrm">e</span><span class="mord mathrm">c</span><span class="mord mathrm">a</span><span class="mord mathrm">l</span><span class="mord mathrm">l</span><span class="mord mathrm">@</span></span><span class="mord mathrm">2</span><span class="mrel">=</span><span class="mord mathrm">1</span><span class="mord mathrm">/</span><span class="mord mathrm">3</span><span class="mrel">≈</span><span class="mord mathrm">0</span><span class="mord mathrm">.</span><span class="mord mathrm">3</span><span class="mord mathrm">3</span><span class="mord mathrm">3</span></span></span></span>.</p>
+</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:1.448331em;"></span><span class="strut bottom" style="height:2.384331em;vertical-align:-0.936em;"></span><span class="base displaystyle textstyle uncramped"><span class="mord displaystyle textstyle uncramped"><span class="mord mathrm">R</span><span class="mord mathrm">e</span><span class="mord mathrm">c</span><span class="mord mathrm">a</span><span class="mord mathrm">l</span><span class="mord mathrm">l</span><span class="mord mathrm">@</span></span><span class="mord mathit" style="margin-right:0.03148em;">k</span><span class="mrel">=</span><span class="mord reset-textstyle displaystyle textstyle uncramped"><span class="mopen sizing reset-size5 size5 reset-textstyle textstyle uncramped nulldelimiter"></span><span class="mfrac"><span class="vlist"><span style="top:0.686em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></s
pan><span class="reset-textstyle textstyle cramped"><span class="mord textstyle cramped"><span class="mord mathrm">∣</span><span class="mord"><span class="mord textstyle cramped"><span class="mord mathcal" style="margin-right:0.07382em;">I</span></span><span class="msupsub"><span class="vlist"><span style="top:0.247em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped mtight"><span class="mord mathit mtight">u</span></span></span><span style="top:-0.28900000000000003em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped mtight"><span class="mbin mtight">+</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span></span><span
class="mord mathrm">∣</span></span></span></span><span style="top:-0.2300000000000001em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle textstyle uncramped frac-line"></span></span><span style="top:-0.677em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle textstyle uncramped"><span class="mord textstyle uncramped"><span class="mord mathrm">∣</span><span class="mord"><span class="mord textstyle uncramped"><span class="mord mathcal" style="margin-right:0.07382em;">I</span></span><span class="msupsub"><span class="vlist"><span style="top:0.247em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped mtight"><span class="mord mathit mtight">u</span></span></span><span style="top:-0.363em;margin-ri
ght:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle uncramped mtight"><span class="mbin mtight">+</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span></span><span class="mbin">∩</span><span class="mord"><span class="mord mathit" style="margin-right:0.07847em;">I</span><span class="msupsub"><span class="vlist"><span style="top:0.15em;margin-right:0.05em;margin-left:-0.07847em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped mtight"><span class="mord mathit mtight" style="margin-right:0.03148em;">k</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</spa
n></span></span></span><span class="mopen">(</span><span class="mord mathit">u</span><span class="mclose">)</span><span class="mord mathrm">∣</span></span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span><span class="mclose sizing reset-size5 size5 reset-textstyle textstyle uncramped nulldelimiter"></span></span><span class="mord mathrm">.</span></span></span></span></span>
+Here, <span class="katex"><span class="katex-mathml"><math><semantics><mrow><mi mathvariant="normal">∣</mi><msubsup><mrow><mi mathvariant="script">I</mi></mrow><mi>u</mi><mo>+</mo></msubsup><mo>∩</mo><msub><mi>I</mi><mi>k</mi></msub><mo>(</mo><mi>u</mi><mo>)</mo><mi mathvariant="normal">∣</mi></mrow><annotation encoding="application/x-tex">|\mathcal{I}^+_u \cap I_k(u)|</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.771331em;"></span><span class="strut bottom" style="height:1.021331em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class="mord mathrm">∣</span><span class="mord"><span class="mord textstyle uncramped"><span class="mord mathcal" style="margin-right:0.07382em;">I</span></span><span class="msupsub"><span class="vlist"><span style="top:0.247em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;"> 
0B;</span></span><span class="reset-textstyle scriptstyle cramped mtight"><span class="mord mathit mtight">u</span></span></span><span style="top:-0.363em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle uncramped mtight"><span class="mbin mtight">+</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span></span><span class="mbin">∩</span><span class="mord"><span class="mord mathit" style="margin-right:0.07847em;">I</span><span class="msupsub"><span class="vlist"><span style="top:0.15em;margin-right:0.05em;margin-left:-0.07847em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped mtight"><span class="mord mathit mtight" style="margin-right:0.03148em;
">k</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span></span><span class="mopen">(</span><span class="mord mathit">u</span><span class="mclose">)</span><span class="mord mathrm">∣</span></span></span></span> is the number of true positives. If <span class="katex"><span class="katex-mathml"><math><semantics><mrow><msub><mi>I</mi><mn>2</mn></msub><mo>(</mo><mi>u</mi><mo>)</mo><mo>=</mo><mo>{</mo><mn>1</mn><mo separator="true">,</mo><mn>3</mn><mo>}</mo></mrow><annotation encoding="application/x-tex">I_2(u) = \{1, 3\}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.75em;"></span><span class="strut bottom" style="height:1em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class="mord"><span class="mord mathit" style="margin-right:0.07847em;">I</span><span class
="msupsub"><span class="vlist"><span style="top:0.15em;margin-right:0.05em;margin-left:-0.07847em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped mtight"><span class="mord mathrm mtight">2</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span></span><span class="mopen">(</span><span class="mord mathit">u</span><span class="mclose">)</span><span class="mrel">=</span><span class="mopen">{</span><span class="mord mathrm">1</span><span class="mpunct">,</span><span class="mord mathrm">3</span><span class="mclose">}</span></span></span></span> and <span class="katex"><span class="katex-mathml"><math><semantics><mrow><msubsup><mrow><mi mathvariant="script">I</mi></mrow><mi>u</mi><mo>+</mo></msubsup><mo>=</mo><mo>{</mo><mn>1</mn><mo separator="true">,</mo><mn>2</mn><mo
separator="true">,</mo><mn>4</mn><mo>}</mo></mrow><annotation encoding="application/x-tex">\mathcal{I}^+_u = \{1, 2, 4\}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.771331em;"></span><span class="strut bottom" style="height:1.021331em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class="mord"><span class="mord textstyle uncramped"><span class="mord mathcal" style="margin-right:0.07382em;">I</span></span><span class="msupsub"><span class="vlist"><span style="top:0.247em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped mtight"><span class="mord mathit mtight">u</span></span></span><span style="top:-0.363em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scripts
tyle uncramped mtight"><span class="mbin mtight">+</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span></span><span class="mrel">=</span><span class="mopen">{</span><span class="mord mathrm">1</span><span class="mpunct">,</span><span class="mord mathrm">2</span><span class="mpunct">,</span><span class="mord mathrm">4</span><span class="mclose">}</span></span></span></span>, <span class="katex"><span class="katex-mathml"><math><semantics><mrow><mrow><mi mathvariant="normal">R</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">c</mi><mi mathvariant="normal">a</mi><mi mathvariant="normal">l</mi><mi mathvariant="normal">l</mi><mi mathvariant="normal">@</mi></mrow><mn>2</mn><mo>=</mo><mn>1</mn><mi mathvariant="normal">/</mi><mn>3</mn><mo>≈</mo><mn>0</mn><mi mathvariant="normal">.</mi><mn>3</mn><mn>3</mn><mn>3</mn></mrow><annotation encoding="applicat
ion/x-tex">\mathrm{Recall@}2 = 1 / 3 \approx 0.333</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.75em;"></span><span class="strut bottom" style="height:1em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class="mord textstyle uncramped"><span class="mord mathrm">R</span><span class="mord mathrm">e</span><span class="mord mathrm">c</span><span class="mord mathrm">a</span><span class="mord mathrm">l</span><span class="mord mathrm">l</span><span class="mord mathrm">@</span></span><span class="mord mathrm">2</span><span class="mrel">=</span><span class="mord mathrm">1</span><span class="mord mathrm">/</span><span class="mord mathrm">3</span><span class="mrel">≈</span><span class="mord mathrm">0</span><span class="mord mathrm">.</span><span class="mord mathrm">3</span><span class="mord mathrm">3</span><span class="mord mathrm">3</span></span></span></span>.</p>
<h2 id="precision-at-k">Precision-At-k</h2>
-<p>Unlike Recall@k, <strong>Precision-at-k (Precision@k)</strong> evaluates correctness of a top-k recommendation list <span class="katex"><span class="katex-mathml"><math><semantics><mrow><msub><mi>I</mi><mi>k</mi></msub><mo>(</mo><mi>u</mi><mo>)</mo></mrow><annotation encoding="application/x-tex">I_k(u)</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.75em;"></span><span class="strut bottom" style="height:1em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class="mord"><span class="mord mathit" style="margin-right:0.07847em;">I</span><span class="vlist"><span style="top:0.15em;margin-right:0.05em;margin-left:-0.07847em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped"><span class="mord mathit" style="margin-right:0.03148em;">k</span></span></span><span class="baseline-fix"><span class
="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span><span class="mopen">(</span><span class="mord mathit">u</span><span class="mclose">)</span></span></span></span> according to the portion of true positives in the list as:
+<p>Unlike Recall@k, <strong>Precision-at-k (Precision@k)</strong> evaluates correctness of a top-k recommendation list <span class="katex"><span class="katex-mathml"><math><semantics><mrow><msub><mi>I</mi><mi>k</mi></msub><mo>(</mo><mi>u</mi><mo>)</mo></mrow><annotation encoding="application/x-tex">I_k(u)</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.75em;"></span><span class="strut bottom" style="height:1em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class="mord"><span class="mord mathit" style="margin-right:0.07847em;">I</span><span class="msupsub"><span class="vlist"><span style="top:0.15em;margin-right:0.05em;margin-left:-0.07847em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped mtight"><span class="mord mathit mtight" style="margin-right:0.03148em;">k</span></span></span><s
pan class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span></span><span class="mopen">(</span><span class="mord mathit">u</span><span class="mclose">)</span></span></span></span> according to the portion of true positives in the list as:
<span class="katex-display"><span class="katex"><span class="katex-mathml"><math><semantics><mrow><mrow><mi mathvariant="normal">P</mi><mi mathvariant="normal">r</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">c</mi><mi mathvariant="normal">i</mi><mi mathvariant="normal">s</mi><mi mathvariant="normal">i</mi><mi mathvariant="normal">o</mi><mi mathvariant="normal">n</mi><mi mathvariant="normal">@</mi></mrow><mi>k</mi><mo>=</mo><mfrac><mrow><mi mathvariant="normal">∣</mi><msubsup><mrow><mi mathvariant="script">I</mi></mrow><mi>u</mi><mo>+</mo></msubsup><mo>∩</mo><msub><mi>I</mi><mi>k</mi></msub><mo>(</mo><mi>u</mi><mo>)</mo><mi mathvariant="normal">∣</mi></mrow><mrow><mi mathvariant="normal">∣</mi><msub><mi>I</mi><mi>k</mi></msub><mo>(</mo><mi>u</mi><mo>)</mo><mi mathvariant="normal">∣</mi></mrow></mfrac><mi mathvariant="normal">.</mi></mrow><annotation encoding="application/x-tex">
\mathrm{Precision@}k = \frac{|\mathcal{I}^+_u \cap I_k(u)|}{|I_k(u)|}.
-</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:1.448331em;"></span><span class="strut bottom" style="height:2.384331em;vertical-align:-0.936em;"></span><span class="base displaystyle textstyle uncramped"><span class="mord displaystyle textstyle uncramped"><span class="mord mathrm">P</span><span class="mord mathrm">r</span><span class="mord mathrm">e</span><span class="mord mathrm">c</span><span class="mord mathrm">i</span><span class="mord mathrm">s</span><span class="mord mathrm">i</span><span class="mord mathrm">o</span><span class="mord mathrm">n</span><span class="mord mathrm">@</span></span><span class="mord mathit" style="margin-right:0.03148em;">k</span><span class="mrel">=</span><span class="mord reset-textstyle displaystyle textstyle uncramped"><span class="sizing reset-size5 size5 reset-textstyle textstyle uncramped nulldelimiter"></span><span class="mfrac"><span class="vlist"><span style="top:0.686em;">
<span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle textstyle cramped"><span class="mord textstyle cramped"><span class="mord mathrm">∣</span><span class="mord"><span class="mord mathit" style="margin-right:0.07847em;">I</span><span class="vlist"><span style="top:0.15em;margin-right:0.05em;margin-left:-0.07847em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped"><span class="mord mathit" style="margin-right:0.03148em;">k</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span><span class="mopen">(</span><span class="mord mathit">u</span><span class="mclose">)</span><span class="mord mathrm">∣</span></span></span></span><span style="top:-0.2300000000000001em;"><span class="font
size-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle textstyle uncramped frac-line"></span></span><span style="top:-0.677em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle textstyle uncramped"><span class="mord textstyle uncramped"><span class="mord mathrm">∣</span><span class=""><span class="mord textstyle uncramped"><span class="mord mathcal" style="margin-right:0.07382em;">I</span></span><span class="vlist"><span style="top:0.247em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped"><span class="mord mathit">u</span></span></span><span style="top:-0.363em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle
uncramped"><span class="mord">+</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span><span class="mbin">∩</span><span class="mord"><span class="mord mathit" style="margin-right:0.07847em;">I</span><span class="vlist"><span style="top:0.15em;margin-right:0.05em;margin-left:-0.07847em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped"><span class="mord mathit" style="margin-right:0.03148em;">k</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span><span class="mopen">(</span><span class="mord mathit">u</span><span class="mclose">)</span><span class="mord mathrm">∣</span></span></span></span><span class="baseline-fix"><span class="fo
ntsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span><span class="sizing reset-size5 size5 reset-textstyle textstyle uncramped nulldelimiter"></span></span><span class="mord mathrm">.</span></span></span></span></span>
-In other words, Precision@k means how much the recommendation list covers true pairs. Here, <span class="katex"><span class="katex-mathml"><math><semantics><mrow><mrow><mi mathvariant="normal">P</mi><mi mathvariant="normal">r</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">c</mi><mi mathvariant="normal">i</mi><mi mathvariant="normal">s</mi><mi mathvariant="normal">i</mi><mi mathvariant="normal">o</mi><mi mathvariant="normal">n</mi><mi mathvariant="normal">@</mi></mrow><mn>2</mn><mo>=</mo><mn>1</mn><mi mathvariant="normal">/</mi><mn>2</mn><mo>=</mo><mn>0</mn><mi mathvariant="normal">.</mi><mn>5</mn></mrow><annotation encoding="application/x-tex">\mathrm{Precision@}2 = 1 / 2 = 0.5</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.75em;"></span><span class="strut bottom" style="height:1em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class="mord textstyle uncramped"><span clas
s="mord mathrm">P</span><span class="mord mathrm">r</span><span class="mord mathrm">e</span><span class="mord mathrm">c</span><span class="mord mathrm">i</span><span class="mord mathrm">s</span><span class="mord mathrm">i</span><span class="mord mathrm">o</span><span class="mord mathrm">n</span><span class="mord mathrm">@</span></span><span class="mord mathrm">2</span><span class="mrel">=</span><span class="mord mathrm">1</span><span class="mord mathrm">/</span><span class="mord mathrm">2</span><span class="mrel">=</span><span class="mord mathrm">0</span><span class="mord mathrm">.</span><span class="mord mathrm">5</span></span></span></span> where <span class="katex"><span class="katex-mathml"><math><semantics><mrow><msub><mi>I</mi><mn>2</mn></msub><mo>(</mo><mi>u</mi><mo>)</mo><mo>=</mo><mo>{</mo><mn>1</mn><mo separator="true">,</mo><mn>3</mn><mo>}</mo></mrow><annotation encoding="application/x-tex">I_2(u) = \{1, 3\}</annotation></semantics></math></span><span class="katex-html" a
ria-hidden="true"><span class="strut" style="height:0.75em;"></span><span class="strut bottom" style="height:1em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class="mord"><span class="mord mathit" style="margin-right:0.07847em;">I</span><span class="vlist"><span style="top:0.15em;margin-right:0.05em;margin-left:-0.07847em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped"><span class="mord mathrm">2</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span><span class="mopen">(</span><span class="mord mathit">u</span><span class="mclose">)</span><span class="mrel">=</span><span class="mopen">{</span><span class="mord mathrm">1</span><span class="mpunct">,</span><span class="mord mathrm">3</span><span class="mclose">}</span></span></span
></span> and <span class="katex"><span class="katex-mathml"><math><semantics><mrow><msubsup><mrow><mi mathvariant="script">I</mi></mrow><mi>u</mi><mo>+</mo></msubsup><mo>=</mo><mo>{</mo><mn>1</mn><mo separator="true">,</mo><mn>2</mn><mo separator="true">,</mo><mn>4</mn><mo>}</mo></mrow><annotation encoding="application/x-tex">\mathcal{I}^+_u = \{1, 2, 4\}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.771331em;"></span><span class="strut bottom" style="height:1.021331em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class=""><span class="mord textstyle uncramped"><span class="mord mathcal" style="margin-right:0.07382em;">I</span></span><span class="vlist"><span style="top:0.247em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped"><span class="mord mathit">u</span><
/span></span><span style="top:-0.363em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle uncramped"><span class="mord">+</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span><span class="mrel">=</span><span class="mopen">{</span><span class="mord mathrm">1</span><span class="mpunct">,</span><span class="mord mathrm">2</span><span class="mpunct">,</span><span class="mord mathrm">4</span><span class="mclose">}</span></span></span></span>.</p>
+</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:1.448331em;"></span><span class="strut bottom" style="height:2.384331em;vertical-align:-0.936em;"></span><span class="base displaystyle textstyle uncramped"><span class="mord displaystyle textstyle uncramped"><span class="mord mathrm">P</span><span class="mord mathrm">r</span><span class="mord mathrm">e</span><span class="mord mathrm">c</span><span class="mord mathrm">i</span><span class="mord mathrm">s</span><span class="mord mathrm">i</span><span class="mord mathrm">o</span><span class="mord mathrm">n</span><span class="mord mathrm">@</span></span><span class="mord mathit" style="margin-right:0.03148em;">k</span><span class="mrel">=</span><span class="mord reset-textstyle displaystyle textstyle uncramped"><span class="mopen sizing reset-size5 size5 reset-textstyle textstyle uncramped nulldelimiter"></span><span class="mfrac"><span class="vlist"><span style="top:0.68
6em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle textstyle cramped"><span class="mord textstyle cramped"><span class="mord mathrm">∣</span><span class="mord"><span class="mord mathit" style="margin-right:0.07847em;">I</span><span class="msupsub"><span class="vlist"><span style="top:0.15em;margin-right:0.05em;margin-left:-0.07847em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped mtight"><span class="mord mathit mtight" style="margin-right:0.03148em;">k</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span></span><span class="mopen">(</span><span class="mord mathit">u</span><span class="mclose">)</span><span class="mord mathrm">∣</span></span></span></span><span sty
le="top:-0.2300000000000001em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle textstyle uncramped frac-line"></span></span><span style="top:-0.677em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle textstyle uncramped"><span class="mord textstyle uncramped"><span class="mord mathrm">∣</span><span class="mord"><span class="mord textstyle uncramped"><span class="mord mathcal" style="margin-right:0.07382em;">I</span></span><span class="msupsub"><span class="vlist"><span style="top:0.247em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped mtight"><span class="mord mathit mtight">u</span></span></span><span style="top:-0.363em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><sp
an style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle uncramped mtight"><span class="mbin mtight">+</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span></span><span class="mbin">∩</span><span class="mord"><span class="mord mathit" style="margin-right:0.07847em;">I</span><span class="msupsub"><span class="vlist"><span style="top:0.15em;margin-right:0.05em;margin-left:-0.07847em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped mtight"><span class="mord mathit mtight" style="margin-right:0.03148em;">k</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span></span><span class="mopen">(</span><span class="m
ord mathit">u</span><span class="mclose">)</span><span class="mord mathrm">∣</span></span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span><span class="mclose sizing reset-size5 size5 reset-textstyle textstyle uncramped nulldelimiter"></span></span><span class="mord mathrm">.</span></span></span></span></span>
+In other words, Precision@k means how much the recommendation list covers true pairs. Here, <span class="katex"><span class="katex-mathml"><math><semantics><mrow><mrow><mi mathvariant="normal">P</mi><mi mathvariant="normal">r</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">c</mi><mi mathvariant="normal">i</mi><mi mathvariant="normal">s</mi><mi mathvariant="normal">i</mi><mi mathvariant="normal">o</mi><mi mathvariant="normal">n</mi><mi mathvariant="normal">@</mi></mrow><mn>2</mn><mo>=</mo><mn>1</mn><mi mathvariant="normal">/</mi><mn>2</mn><mo>=</mo><mn>0</mn><mi mathvariant="normal">.</mi><mn>5</mn></mrow><annotation encoding="application/x-tex">\mathrm{Precision@}2 = 1 / 2 = 0.5</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.75em;"></span><span class="strut bottom" style="height:1em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class="mord textstyle uncramped"><span clas
s="mord mathrm">P</span><span class="mord mathrm">r</span><span class="mord mathrm">e</span><span class="mord mathrm">c</span><span class="mord mathrm">i</span><span class="mord mathrm">s</span><span class="mord mathrm">i</span><span class="mord mathrm">o</span><span class="mord mathrm">n</span><span class="mord mathrm">@</span></span><span class="mord mathrm">2</span><span class="mrel">=</span><span class="mord mathrm">1</span><span class="mord mathrm">/</span><span class="mord mathrm">2</span><span class="mrel">=</span><span class="mord mathrm">0</span><span class="mord mathrm">.</span><span class="mord mathrm">5</span></span></span></span> where <span class="katex"><span class="katex-mathml"><math><semantics><mrow><msub><mi>I</mi><mn>2</mn></msub><mo>(</mo><mi>u</mi><mo>)</mo><mo>=</mo><mo>{</mo><mn>1</mn><mo separator="true">,</mo><mn>3</mn><mo>}</mo></mrow><annotation encoding="application/x-tex">I_2(u) = \{1, 3\}</annotation></semantics></math></span><span class="katex-html" a
ria-hidden="true"><span class="strut" style="height:0.75em;"></span><span class="strut bottom" style="height:1em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class="mord"><span class="mord mathit" style="margin-right:0.07847em;">I</span><span class="msupsub"><span class="vlist"><span style="top:0.15em;margin-right:0.05em;margin-left:-0.07847em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped mtight"><span class="mord mathrm mtight">2</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span></span><span class="mopen">(</span><span class="mord mathit">u</span><span class="mclose">)</span><span class="mrel">=</span><span class="mopen">{</span><span class="mord mathrm">1</span><span class="mpunct">,</span><span class="mord mathrm">3</span
><span class="mclose">}</span></span></span></span> and <span class="katex"><span class="katex-mathml"><math><semantics><mrow><msubsup><mrow><mi mathvariant="script">I</mi></mrow><mi>u</mi><mo>+</mo></msubsup><mo>=</mo><mo>{</mo><mn>1</mn><mo separator="true">,</mo><mn>2</mn><mo separator="true">,</mo><mn>4</mn><mo>}</mo></mrow><annotation encoding="application/x-tex">\mathcal{I}^+_u = \{1, 2, 4\}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.771331em;"></span><span class="strut bottom" style="height:1.021331em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class="mord"><span class="mord textstyle uncramped"><span class="mord mathcal" style="margin-right:0.07382em;">I</span></span><span class="msupsub"><span class="vlist"><span style="top:0.247em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="res
et-textstyle scriptstyle cramped mtight"><span class="mord mathit mtight">u</span></span></span><span style="top:-0.363em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle uncramped mtight"><span class="mbin mtight">+</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span></span><span class="mrel">=</span><span class="mopen">{</span><span class="mord mathrm">1</span><span class="mpunct">,</span><span class="mord mathrm">2</span><span class="mpunct">,</span><span class="mord mathrm">4</span><span class="mclose">}</span></span></span></span>.</p>
<h2 id="mean-average-precision-map">Mean Average Precision (MAP)</h2>
-<p>While the original Precision@k provides a score for a fixed-length recommendation list <span class="katex"><span class="katex-mathml"><math><semantics><mrow><msub><mi>I</mi><mi>k</mi></msub><mo>(</mo><mi>u</mi><mo>)</mo></mrow><annotation encoding="application/x-tex">I_k(u)</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.75em;"></span><span class="strut bottom" style="height:1em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class="mord"><span class="mord mathit" style="margin-right:0.07847em;">I</span><span class="vlist"><span style="top:0.15em;margin-right:0.05em;margin-left:-0.07847em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped"><span class="mord mathit" style="margin-right:0.03148em;">k</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size
5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span><span class="mopen">(</span><span class="mord mathit">u</span><span class="mclose">)</span></span></span></span>, <strong>mean average precision (MAP)</strong> computes an average of the scores over all recommendation sizes from 1 to <span class="katex"><span class="katex-mathml"><math><semantics><mrow><mi mathvariant="normal">∣</mi><mrow><mi mathvariant="script">I</mi></mrow><mi mathvariant="normal">∣</mi></mrow><annotation encoding="application/x-tex">|\mathcal{I}|</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.75em;"></span><span class="strut bottom" style="height:1em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class="mord mathrm">∣</span><span class="mord textstyle uncramped"><span class="mord mathcal" style="margin-right:0.07382em;">I</span></span><span class="mord ma
thrm">∣</span></span></span></span>. MAP is formulated with an indicator function for <span class="katex"><span class="katex-mathml"><math><semantics><mrow><msub><mi>i</mi><mi>n</mi></msub></mrow><annotation encoding="application/x-tex">i_n</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.65952em;"></span><span class="strut bottom" style="height:0.80952em;vertical-align:-0.15em;"></span><span class="base textstyle uncramped"><span class="mord"><span class="mord mathit">i</span><span class="vlist"><span style="top:0.15em;margin-right:0.05em;margin-left:0em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped"><span class="mord mathit">n</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span></s
pan></span></span> (the <span class="katex"><span class="katex-mathml"><math><semantics><mrow><mi>n</mi></mrow><annotation encoding="application/x-tex">n</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.43056em;"></span><span class="strut bottom" style="height:0.43056em;vertical-align:0em;"></span><span class="base textstyle uncramped"><span class="mord mathit">n</span></span></span></span>-th item of <span class="katex"><span class="katex-mathml"><math><semantics><mrow><mi>I</mi><mo>(</mo><mi>u</mi><mo>)</mo></mrow><annotation encoding="application/x-tex">I(u)</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.75em;"></span><span class="strut bottom" style="height:1em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class="mord mathit" style="margin-right:0.07847em;">I</span><span class="mopen">(</span><span class="mord
mathit">u</span><span class="mclose">)</span></span></span></span>), as:
+<p>While the original Precision@k provides a score for a fixed-length recommendation list <span class="katex"><span class="katex-mathml"><math><semantics><mrow><msub><mi>I</mi><mi>k</mi></msub><mo>(</mo><mi>u</mi><mo>)</mo></mrow><annotation encoding="application/x-tex">I_k(u)</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.75em;"></span><span class="strut bottom" style="height:1em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class="mord"><span class="mord mathit" style="margin-right:0.07847em;">I</span><span class="msupsub"><span class="vlist"><span style="top:0.15em;margin-right:0.05em;margin-left:-0.07847em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped mtight"><span class="mord mathit mtight" style="margin-right:0.03148em;">k</span></span></span><span class="baseline-fix"><spa
n class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span></span><span class="mopen">(</span><span class="mord mathit">u</span><span class="mclose">)</span></span></span></span>, <strong>mean average precision (MAP)</strong> computes an average of the scores over all recommendation sizes from 1 to <span class="katex"><span class="katex-mathml"><math><semantics><mrow><mi mathvariant="normal">∣</mi><mrow><mi mathvariant="script">I</mi></mrow><mi mathvariant="normal">∣</mi></mrow><annotation encoding="application/x-tex">|\mathcal{I}|</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.75em;"></span><span class="strut bottom" style="height:1em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class="mord mathrm">∣</span><span class="mord textstyle uncramped"><span class="mord mathcal" style="margin-right:0.07
382em;">I</span></span><span class="mord mathrm">∣</span></span></span></span>. MAP is formulated with an indicator function for <span class="katex"><span class="katex-mathml"><math><semantics><mrow><msub><mi>i</mi><mi>n</mi></msub></mrow><annotation encoding="application/x-tex">i_n</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.65952em;"></span><span class="strut bottom" style="height:0.80952em;vertical-align:-0.15em;"></span><span class="base textstyle uncramped"><span class="mord"><span class="mord mathit">i</span><span class="msupsub"><span class="vlist"><span style="top:0.15em;margin-right:0.05em;margin-left:0em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped mtight"><span class="mord mathit mtight">n</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><spa
n style="font-size:0em;">​</span></span>​</span></span></span></span></span></span></span> (the <span class="katex"><span class="katex-mathml"><math><semantics><mrow><mi>n</mi></mrow><annotation encoding="application/x-tex">n</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.43056em;"></span><span class="strut bottom" style="height:0.43056em;vertical-align:0em;"></span><span class="base textstyle uncramped"><span class="mord mathit">n</span></span></span></span>-th item of <span class="katex"><span class="katex-mathml"><math><semantics><mrow><mi>I</mi><mo>(</mo><mi>u</mi><mo>)</mo></mrow><annotation encoding="application/x-tex">I(u)</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:0.75em;"></span><span class="strut bottom" style="height:1em;vertical-align:-0.25em;"></span><span class="base textstyle uncramped"><span class="mord mathit"
style="margin-right:0.07847em;">I</span><span class="mopen">(</span><span class="mord mathit">u</span><span class="mclose">)</span></span></span></span>), as:
<span class="katex-display"><span class="katex"><span class="katex-mathml"><math><semantics><mrow><mrow><mi mathvariant="normal">M</mi><mi mathvariant="normal">A</mi><mi mathvariant="normal">P</mi></mrow><mo>=</mo><mfrac><mrow><mn>1</mn></mrow><mrow><mi mathvariant="normal">∣</mi><msubsup><mrow><mi mathvariant="script">I</mi></mrow><mi>u</mi><mo>+</mo></msubsup><mi mathvariant="normal">∣</mi></mrow></mfrac><msubsup><mo>∑</mo><mrow><mi>n</mi><mo>=</mo><mn>1</mn></mrow><mrow><mi mathvariant="normal">∣</mi><mrow><mi mathvariant="script">I</mi></mrow><mi mathvariant="normal">∣</mi></mrow></msubsup><mrow><mi mathvariant="normal">P</mi><mi mathvariant="normal">r</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">c</mi><mi mathvariant="normal">i</mi><mi mathvariant="normal">s</mi><mi mathvariant="normal">i</mi><mi mathvariant="normal">o</mi><mi mathvariant="normal">n</mi><mi mathvariant="normal">@</mi></mrow><mi>n</mi><mo>⋅</mo><mo>[</mo><
msub><mi>i</mi><mi>n</mi></msub><mo>∈</mo><msubsup><mrow><mi mathvariant="script">I</mi></mrow><mi>u</mi><mo>+</mo></msubsup><mo>]</mo><mi mathvariant="normal">.</mi></mrow><annotation encoding="application/x-tex">
\mathrm{MAP} = \frac{1}{|\mathcal{I}^+_u|} \sum_{n = 1}^{|\mathcal{I}|} \mathrm{Precision@}n \cdot [ i_n \in \mathcal{I}^+_u ].
-</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:1.9610050000000003em;"></span><span class="strut bottom" style="height:3.2281180000000003em;vertical-align:-1.267113em;"></span><span class="base displaystyle textstyle uncramped"><span class="mord displaystyle textstyle uncramped"><span class="mord mathrm">M</span><span class="mord mathrm">A</span><span class="mord mathrm">P</span></span><span class="mrel">=</span><span class="mord reset-textstyle displaystyle textstyle uncramped"><span class="sizing reset-size5 size5 reset-textstyle textstyle uncramped nulldelimiter"></span><span class="mfrac"><span class="vlist"><span style="top:0.686em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle textstyle cramped"><span class="mord textstyle cramped"><span class="mord mathrm">∣</span><span class=""><span class="mord textstyle cramped"><sp
an class="mord mathcal" style="margin-right:0.07382em;">I</span></span><span class="vlist"><span style="top:0.247em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped"><span class="mord mathit">u</span></span></span><span style="top:-0.29733em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped"><span class="mord">+</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span><span class="mord mathrm">∣</span></span></span></span><span style="top:-0.2300000000000001em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle textstyle uncramped frac-line"><
/span></span><span style="top:-0.677em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle textstyle uncramped"><span class="mord textstyle uncramped"><span class="mord mathrm">1</span></span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span><span class="sizing reset-size5 size5 reset-textstyle textstyle uncramped nulldelimiter"></span></span><span class="mop op-limits"><span class="vlist"><span style="top:1.1671129999999998em;margin-left:0em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped"><span class="mord scriptstyle cramped"><span class="mord mathit">n</span><span class="mrel">=</span><span class="mord mathrm">1</span></span></span></span><span style="top:-0.000005000000000143778em;
"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span><span class="op-symbol large-op mop">∑</span></span></span><span style="top:-1.3360050000000003em;margin-left:0em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle uncramped"><span class="mord scriptstyle uncramped"><span class="mord mathrm">∣</span><span class="mord scriptstyle uncramped"><span class="mord mathcal" style="margin-right:0.07382em;">I</span></span><span class="mord mathrm">∣</span></span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span><span class="mord displaystyle textstyle uncramped"><span class="mord mathrm">P</span><span class="mord mathrm">r</span><span class="mord mathrm">e</span><span class="mord mathrm">c</span><span class
="mord mathrm">i</span><span class="mord mathrm">s</span><span class="mord mathrm">i</span><span class="mord mathrm">o</span><span class="mord mathrm">n</span><span class="mord mathrm">@</span></span><span class="mord mathit">n</span><span class="mbin">⋅</span><span class="mopen">[</span><span class="mord"><span class="mord mathit">i</span><span class="vlist"><span style="top:0.15em;margin-right:0.05em;margin-left:0em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped"><span class="mord mathit">n</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span><span class="mrel">∈</span><span class=""><span class="mord displaystyle textstyle uncramped"><span class="mord mathcal" style="margin-right:0.07382em;">I</span></span><span class="vlist"><span style="top:
0.247em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped"><span class="mord mathit">u</span></span></span><span style="top:-0.4129999999999999em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle uncramped"><span class="mord">+</span></span></span><span class="baseline-fix"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span>​</span></span></span><span class="mclose">]</span><span class="mord mathrm">.</span></span></span></span></span></p>
+</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="strut" style="height:1.9610050000000003em;"></span><span class="strut bottom" style="height:3.2281180000000003em;vertical-align:-1.267113em;"></span><span class="base displaystyle textstyle uncramped"><span class="mord displaystyle textstyle uncramped"><span class="mord mathrm">M</span><span class="mord mathrm">A</span><span class="mord mathrm">P</span></span><span class="mrel">=</span><span class="mord reset-textstyle displaystyle textstyle uncramped"><span class="mopen sizing reset-size5 size5 reset-textstyle textstyle uncramped nulldelimiter"></span><span class="mfrac"><span class="vlist"><span style="top:0.686em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle textstyle cramped"><span class="mord textstyle cramped"><span class="mord mathrm">∣</span><span class="mord"><span class="mord textstyle cr
amped"><span class="mord mathcal" style="margin-right:0.07382em;">I</span></span><span class="msupsub"><span class="vlist"><span style="top:0.247em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="font-size:0em;">​</span></span><span class="reset-textstyle scriptstyle cramped mtight"><span class="mord mathit mtight">u</span></span></span><span style="top:-0.28900000000000003em;margin-right:0.05em;"><span class="fontsize-ensurer reset-size5 size5"><span style="fo
<TRUNCATED>