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Posted to issues@spark.apache.org by "Joseph K. Bradley (JIRA)" <ji...@apache.org> on 2015/12/17 02:53:46 UTC
[jira] [Updated] (SPARK-12372) Document limitations of MLlib linear
algebra
[ https://issues.apache.org/jira/browse/SPARK-12372?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Joseph K. Bradley updated SPARK-12372:
--------------------------------------
Component/s: (was: PySpark)
Documentation
> Document limitations of MLlib linear algebra
> --------------------------------------------
>
> Key: SPARK-12372
> URL: https://issues.apache.org/jira/browse/SPARK-12372
> Project: Spark
> Issue Type: Documentation
> Components: Documentation, MLlib
> Affects Versions: 1.5.2
> Reporter: Christos Iraklis Tsatsoulis
>
> Consider the following snippet in pyspark 1.5.2:
> {code:none}
> >>> from pyspark.mllib.linalg import Vectors
> >>> x = Vectors.dense([0.0, 1.0, 0.0, 7.0, 0.0])
> >>> x
> DenseVector([0.0, 1.0, 0.0, 7.0, 0.0])
> >>> -x
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> TypeError: func() takes exactly 2 arguments (1 given)
> >>> y = Vectors.dense([2.0, 0.0, 3.0, 4.0, 5.0])
> >>> y
> DenseVector([2.0, 0.0, 3.0, 4.0, 5.0])
> >>> x-y
> DenseVector([-2.0, 1.0, -3.0, 3.0, -5.0])
> >>> -y+x
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> TypeError: func() takes exactly 2 arguments (1 given)
> >>> -1*x
> DenseVector([-0.0, -1.0, -0.0, -7.0, -0.0])
> {code}
> Clearly, the unary operator {{-}} (minus) for vectors fails, giving errors for expressions like {{-x}} and {{-y+x}}, despite the fact that {{x-y}} behaves as expected.
> The last operation, {{-1*x}}, although mathematically "correct", includes minus signs for the zero entries, which again is normally not expected.
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