Github user felixcheung commented on a diff in the pull request:
https://github.com/apache/spark/pull/14779#discussion_r76100314
--- Diff: R/pkg/R/functions.R ---
@@ -3194,25 +3206,34 @@ setMethod("lag",
#' lead
#'
#' Window function: returns the value that is \code{offset} rows after the
current row, and
-#' NULL if there is less than \code{offset} rows after the current row.
For example,
-#' an \code{offset} of one will return the next row at any given point in
the window partition.
+#' \code{defaultValue} if there is less than \code{offset} rows after the
current row.
+#' For example, an \code{offset} of one will return the next row at any
given point
+#' in the window partition.
#'
#' This is equivalent to the \code{LEAD} function in SQL.
#'
#' @param x Column to compute on
-#' @param offset Number of rows to offset
+#' @param offset Number of rows to offset. If not specified, the default
is 1.
#' @param defaultValue (Optional) default value to use
#'
#' @rdname lead
#' @name lead
#' @family window_funcs
#' @aliases lead,characterOrColumn,numeric-method
#' @export
-#' @examples \dontrun{lead(df$c)}
+#' @examples \dontrun{
+#' df <- createDataFrame(mtcars)
+#'
+#' # Partition by am (transmission) and order by hp (horsepower)
+#' ws <- orderBy(windowPartitionBy("am"), "hp")
+#'
+#' # Lag mpg values by 1 row on the partition-and-ordered table
--- End diff --
lag -> lead?
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