[SPARK-16508][SPARKR] Split docs for arrange and orderBy methods

## What changes were proposed in this pull request?

This PR splits arrange and orderBy methods according to their functionality (the former for sorting sparkDataFrame and the latter for windowSpec).

## How was this patch tested?

![screen shot 2016-08-06 at 6 39 19 pm](https://cloud.githubusercontent.com/assets/15318264/17459969/51eade28-5c05-11e6-8ca1-8d8a8e344bab.png)
![screen shot 2016-08-06 at 6 39 29 pm](https://cloud.githubusercontent.com/assets/15318264/17459966/51e3c246-5c05-11e6-8d35-3e905ca48676.png)
![screen shot 2016-08-06 at 6 40 02 pm](https://cloud.githubusercontent.com/assets/15318264/17459967/51e650ec-5c05-11e6-8698-0f037f5199ff.png)

Author: Junyang Qian <junyangq@databricks.com>

Closes #14522 from junyangq/SPARK-16508-0.

.gitignore

@@ -82,3 +82,4 @@ spark-warehouse/
 *.Rproj
 *.Rproj.*
 
+.Rproj.user

R/pkg/R/DataFrame.R

@@ -2048,14 +2048,14 @@ setMethod("rename",
 
 setClassUnion("characterOrColumn", c("character", "Column"))
 
-#' Arrange
+#' Arrange Rows by Variables
 #'
 #' Sort a SparkDataFrame by the specified column(s).
 #'
-#' @param x A SparkDataFrame to be sorted.
-#' @param col A character or Column object vector indicating the fields to sort on
-#' @param ... Additional sorting fields
-#' @param decreasing A logical argument indicating sorting order for columns when
+#' @param x a SparkDataFrame to be sorted.
+#' @param col a character or Column object indicating the fields to sort on
+#' @param ... additional sorting fields
+#' @param decreasing a logical argument indicating sorting order for columns when
 #'                   a character vector is specified for col
 #' @return A SparkDataFrame where all elements are sorted.
 #' @family SparkDataFrame functions
@@ -2120,7 +2120,6 @@ setMethod("arrange",
           })
 
 #' @rdname arrange
-#' @name orderBy
 #' @aliases orderBy,SparkDataFrame,characterOrColumn-method
 #' @export
 #' @note orderBy(SparkDataFrame, characterOrColumn) since 1.4.0

R/pkg/R/WindowSpec.R

@@ -82,16 +82,18 @@ setMethod("partitionBy",
             }
           })
 
-#' orderBy
+#' Ordering Columns in a WindowSpec
 #'
 #' Defines the ordering columns in a WindowSpec.
-#'
 #' @param x a WindowSpec
-#' @return a WindowSpec
-#' @rdname arrange
+#' @param col a character or Column object indicating an ordering column
+#' @param ... additional sorting fields
+#' @return A WindowSpec.
 #' @name orderBy
+#' @rdname orderBy
 #' @aliases orderBy,WindowSpec,character-method
 #' @family windowspec_method
+#' @seealso See \link{arrange} for use in sorting a SparkDataFrame
 #' @export
 #' @examples
 #' \dontrun{
@@ -105,7 +107,7 @@ setMethod("orderBy",
             windowSpec(callJMethod(x@sws, "orderBy", col, list(...)))
           })
 
-#' @rdname arrange
+#' @rdname orderBy
 #' @name orderBy
 #' @aliases orderBy,WindowSpec,Column-method
 #' @export
@@ -122,7 +124,7 @@ setMethod("orderBy",
 #' rowsBetween
 #'
 #' Defines the frame boundaries, from `start` (inclusive) to `end` (inclusive).
-#' 
+#'
 #' Both `start` and `end` are relative positions from the current row. For example, "0" means
 #' "current row", while "-1" means the row before the current row, and "5" means the fifth row
 #' after the current row.
@@ -154,7 +156,7 @@ setMethod("rowsBetween",
 #' rangeBetween
 #'
 #' Defines the frame boundaries, from `start` (inclusive) to `end` (inclusive).
-#' 
+#'
 #' Both `start` and `end` are relative from the current row. For example, "0" means "current row",
 #' while "-1" means one off before the current row, and "5" means the five off after the
 #' current row.
@@ -188,7 +190,7 @@ setMethod("rangeBetween",
 
 #' over
 #'
-#' Define a windowing column. 
+#' Define a windowing column.
 #'
 #' @rdname over
 #' @name over

R/pkg/R/generics.R

@@ -551,7 +551,7 @@ setGeneric("merge")
 #' @export
 setGeneric("mutate", function(.data, ...) {standardGeneric("mutate") })
 
-#' @rdname arrange
+#' @rdname orderBy
 #' @export
 setGeneric("orderBy", function(x, col, ...) { standardGeneric("orderBy") })