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Posted to github@arrow.apache.org by "thisisnic (via GitHub)" <gi...@apache.org> on 2023/06/11 16:49:07 UTC
[GitHub] [arrow-cookbook] thisisnic commented on a diff in pull request #311: Document window aggregates
thisisnic commented on code in PR #311:
URL: https://github.com/apache/arrow-cookbook/pull/311#discussion_r1225864495
##########
r/content/tables.Rmd:
##########
@@ -317,4 +317,52 @@ the development version of the Arrow R package had been associated with their op
classes. However, as the Arrow C++ library's functionality extends, compute
functions may be added which do not yet have an R binding. If you find a C++
compute function which you wish to use from the R package, please [open an issue
-on the project JIRA](https://issues.apache.org/jira/projects/ARROW/issues).
\ No newline at end of file
+on the project JIRA](https://issues.apache.org/jira/projects/ARROW/issues).
+
+## Compute Window Aggregates
+
+Arrow does not support window functions, which can be problematic when applying an aggregate like `mean()` on a grouped table or within a rowwise operation like `filter()`:
Review Comment:
Please could you rephrase this to describe the task that the user is trying to achieve (e.g. "you want to...")
##########
r/content/tables.Rmd:
##########
@@ -317,4 +317,52 @@ the development version of the Arrow R package had been associated with their op
classes. However, as the Arrow C++ library's functionality extends, compute
functions may be added which do not yet have an R binding. If you find a C++
compute function which you wish to use from the R package, please [open an issue
-on the project JIRA](https://issues.apache.org/jira/projects/ARROW/issues).
\ No newline at end of file
+on the project JIRA](https://issues.apache.org/jira/projects/ARROW/issues).
+
+## Compute Window Aggregates
+
+Arrow does not support window functions, which can be problematic when applying an aggregate like `mean()` on a grouped table or within a rowwise operation like `filter()`:
+
+```{r, arrow_window_aggregate}
+arrow_table(starwars) %>%
+ select(1:4) %>%
+ filter(!is.na(hair_color)) %>%
+ group_by(hair_color) %>%
+ filter(height < mean(height, na.rm = TRUE))
+```
+
+Arrow pulls the data into R, but for large tables, this sacrifices performance. You can perform these window aggregate operations on Arrow tables by:
+
+- Computing the aggregation separately, and join the result
+- Passing the data to DuckDB
Review Comment:
In terms of following the formula used in other recipes, this would be better suited in the "discussion" section
##########
r/content/tables.Rmd:
##########
@@ -317,4 +317,52 @@ the development version of the Arrow R package had been associated with their op
classes. However, as the Arrow C++ library's functionality extends, compute
functions may be added which do not yet have an R binding. If you find a C++
compute function which you wish to use from the R package, please [open an issue
-on the project JIRA](https://issues.apache.org/jira/projects/ARROW/issues).
\ No newline at end of file
+on the project JIRA](https://issues.apache.org/jira/projects/ARROW/issues).
Review Comment:
Mind also updating this to refer to GH issues instead of JIRA?
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