Github user sun-rui commented on a diff in the pull request:
https://github.com/apache/spark/pull/13760#discussion_r67799929
--- Diff: R/pkg/R/DataFrame.R ---
@@ -1347,6 +1347,65 @@ setMethod("gapply",
gapply(grouped, func, schema)
})
+#' gapplyCollect
+#'
+#' Groups the SparkDataFrame using the specified columns, applies the R
function to each
+#' group and collects the result back to R as data.frame.
+#'
+#' @param x A SparkDataFrame
+#' @rdname gapplyCollect
+#' @name gapplyCollect
+#' @export
+#' @examples
+#'
+#' \dontrun{
+#' Computes the arithmetic mean of the second column by grouping
+#' on the first and third columns. Output the grouping values and the
average.
+#'
+#' result <- gapplyCollect(
+#' df,
+#' list("a", "c"),
+#' function(key, x) {
+#' y <- data.frame(key, mean(x$b), stringsAsFactors = FALSE)
+#' colnames(y) <- c("key_a", "key_c", "mean_b")
+#' y
+#' })
+#'
+#' Result
+#' ------
+#' key_a key_c mean_b
+#' 3 3 3.0
+#' 1 1 1.5
+#'
+#' Fits linear models on iris dataset by grouping on the 'Species' column
and
+#' using 'Sepal_Length' as a target variable, 'Sepal_Width', 'Petal_Length'
+#' and 'Petal_Width' as training features.
+#'
+#' df <- createDataFrame (iris)
+#' result <- gapplyCollect(
+#' df,
+#' list(df$"Species"),
--- End diff --
no need for a scalar to be a list. just df$"Species" is OK.
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