[GitHub] spark pull request: [SPARK-12919][SPARKR] Implement dapply() on Da...

[shivaram <gi...@git.apache.org>]

Github user shivaram commented on a diff in the pull request:

    https://github.com/apache/spark/pull/12493#discussion_r62281013
  
    --- Diff: R/pkg/R/DataFrame.R ---
    @@ -1125,6 +1126,66 @@ setMethod("summarize",
                 agg(x, ...)
               })
     
    +#' dapply
    +#'
    +#' Apply a function to each partition of a DataFrame.
    +#'
    +#' @param x A SparkDataFrame
    +#' @param func A function to be applied to each partition of the SparkDataFrame.
    +#'             func should have only one parameter, to which a data.frame corresponds
    +#'             to each partition will be passed.
    +#'             The output of func should be a data.frame.
    +#' @param schema The schema of the resulting DataFrame after the function is applied.
    +#'               It must match the output of func.
    +#' @family SparkDataFrame functions
    +#' @rdname dapply
    +#' @name dapply
    +#' @export
    +#' @examples
    +#' \dontrun{
    +#'   df <- createDataFrame (sqlContext, iris)
    +#'   df1 <- dapply(df, function(x) { x }, schema(df))
    +#'   collect(df1)
    +#'
    +#'   # filter and add a column
    +#'   df <- createDataFrame (
    +#'           sqlContext, 
    +#'           list(list(1L, 1, "1"), list(2L, 2, "2"), list(3L, 3, "3")),
    +#'           c("a", "b", "c"))
    +#'   schema <- structType(structField("a", "integer"), structField("b", "double"),
    --- End diff --
    
    @sun-rui - Just a note that it'll be great to have the simpler schema specification for 2.0. Let me know if you have a new JIRA or we will use 11046, so we can track it for the release.


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