Github user NarineK commented on a diff in the pull request:
https://github.com/apache/spark/pull/8920#discussion_r40732314
--- Diff: R/pkg/R/DataFrame.R ---
@@ -1848,3 +1848,78 @@ setMethod("crosstab",
sct <- callJMethod(statFunctions, "crosstab", col1, col2)
collect(dataFrame(sct))
})
+
+#' Sort
+#'
+#' Sort a DataFrame by the specified column(s).
+#'
+#' @param x A DataFrame to be sorted.
+#' @param by A character column or Column Object indicating the field to
sort on.
+#' If sorting column is a Column object, we need to embrace the
column with asc or desc
+#' keyword. The 'decreasing' argument does not apply to Column
Object. It only applies to
+#' character column names
+#' @param decreasing Orderings for each sorting column
+#' @param ... Additional sorting fields
+#' @return A DataFrame where elements are sorted by input sorting columns.
+#' @rdname sort
+#' @name sort
+#' @aliases orderby
+#' @export
+#' @examples
+#'\dontrun{
+#' sc <- sparkR.init()
+#' sqlContext <- sparkRSQL.init(sc)
+#' path <- "path/to/file.json"
+#' df <- jsonFile(sqlContext, path)
+#' sort(df, col="col1")
+#' sort(df, decreasing=FALSE, "col2")
+#' sort(df, decreasing=TRUE, "col1")
+#' sort(df, c(TRUE,FALSE), "col1","col2")
+#' sort(df, col=list(asc(df$col1), desc(df$col2)))
+#' sort(df, col=desc(df$col1))
+#' }
+setMethod("sort",
+ signature(x = "DataFrame"),
+ function(x, decreasing=FALSE, col, ...) {
+
+ # all sorting columns
+ by <- c(col, ...)
+
+ if (class(by) == "character"){
+ if (length(decreasing) == 1){
+ # in case only 1 boolean argument - decreasing value is
specified, it will be used for all columns
+ decreasing <- rep(decreasing,length(by))
+ } else if (length(decreasing) != length(by)){
+ stop("Arguments 'col' and 'decreasing' must have the same
length")
+ }
+
+ # creates a string array by replacing TRUE/FALSE
correspondingly by "desc"/"asc"
+ sortOrder <- ifelse (decreasing == FALSE, "asc", decreasing)
+ sortOrder <- ifelse (decreasing == TRUE, "desc", sortOrder)
+
+ # concatenates dataframe with the column names, example:
c("x$Species", "x$Petal_Width")
+ colDFConcat <- paste("x", by, sep = "$")
+
+ # embraces columns with order - asc/desc
+ # example: c("asc(x$Species)", "desc(x$Petal_Length)" )
+ colDFOrderConcat <- paste(sortOrder, "(", colDFConcat, ")",
collapse = ",")
+
+ # concatenates all ordered columns to a list
+ # example: "list(asc(x$Species), desc(x$Petal_Length))"
+ colDFOrderConcatList <- paste("list(", colDFOrderConcat,
")", collapse = "")
+
+ # builds columns of type Column, example: [[1]] Column
Species ASC
+ # [[2]] Column
Petal_Length DESC
+ resCols <- eval(parse(t=colDFOrderConcatList))
--- End diff --
I've made the changes with lapply ... . The code looks more elegant now.
Thank you!
Also, I couldn't directly call arrange, because I have a list of columns
and it doesn't work when I pass a list or an array to arrange(x,col,...). I had
to somehow cast it as three dot and it wasn't feasible. If you know how to do
it and can share it with me that would be great.
Let me know what do you think about my latest commit
Thanks,
Narine
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