jonkeane commented on a change in pull request #9748:
URL: https://github.com/apache/arrow/pull/9748#discussion_r697666647
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File path: r/R/dataset-write.R
##########
@@ -54,6 +54,44 @@
#' - `null_fallback`: character to be used in place of missing values (`NA` or
#' `NULL`) when using Hive-style partitioning. See [hive_partition()].
#' @return The input `dataset`, invisibly
+#' @examplesIf arrow_with_dataset() & arrow_with_parquet() &
requireNamespace("dplyr", quietly = TRUE)
+#' # You can write datasets partitioned by the values in a column (here:
"cyl").
+#' # This creates a structure of the form cyl=X/part-Z.parquet.
+#' one_level_tree <- tempfile()
+#' write_dataset(mtcars, one_level_tree, partitioning = "cyl")
+#' list.files(one_level_tree, recursive = TRUE)
+#'
+#' # You can also partition by the values in multiple columns
+#' # (here: "cyl" and "gear").
+#' # This creates a structure of the form cyl=X/gear=Y/part-Z.parquet.
+#' two_levels_tree <- tempfile()
+#' write_dataset(mtcars, two_levels_tree, partitioning = c("cyl", "gear"))
+#' list.files(two_levels_tree, recursive = TRUE)
+#'
+#' # In the two previous examples we would have:
+#' # X = \{4,6,8\}, the number of cylinders.
+#' # Y = \{3,4,5\}, the number of forward gears.
+#' # Z = \{0,1,2\}, the number of saved parts, starting from 0.
+#'
+#' # You can obtain the same result as as the previous examples using arrow
with
+#' # a dplyr pipeline:
+#'
+#' d <- group_by(mtcars, cyl, gear)
Review comment:
Could we move this line down to between 84 and 85? Also I think it would
be better if it were all in a pipeline (since that's what we're telling people
we are using here):
```
mtcars %>%
group_by(cyl, gear) %>%
write_dataset(two_levels_tree_2)
```
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