Github user shivaram commented on a diff in the pull request:
https://github.com/apache/spark/pull/8266#discussion_r37322106
--- Diff: R/pkg/R/column.R ---
@@ -203,3 +203,49 @@ setMethod("%in%",
jc <- callJMethod(x@jc, "in", table)
return(column(jc))
})
+
+
+#' when
+#'
+#' Evaluates a list of conditions and returns one of multiple possible
result expressions.
+#' If otherwise is not defined at the end, null is returned for unmatched
conditions.
+#'
+#' @rdname column
+setMethod("when",
+ signature(x = "Column", y = "character", z = "ANY"),
+ function(x, y, z) {
+ condition <- y
+ value <- z
+ jc <- callJMethod(x@jc, "when", condition, value)
+ column(jc)
+ })
+
+#' otherwise
+#'
+#' Evaluates a list of conditions and returns one of multiple possible
result expressions.
+#' If otherwise is not defined at the end, null is returned for unmatched
conditions.
+#'
+#' @rdname column
+setMethod("otherwise",
+ signature(x = "Column", value = "ANY"),
+ function(x, value) {
+ value <- ifelse(class(value) == "Column", value@jc, value)
+ jc <- callJMethod(x@jc, "otherwise", value)
+ column(jc)
+ })
+
+#' otherwise
+#'
+#' This is an alias of `otherwise` as an infix operator.
+#'
+#' @rdname column
+#' @aliases otherwise
+#' @examples
+#' \dontrun{
+#' when(df$x > 1 & df$y < 10, 0) %otherwise% 1
+#' }
+setMethod("%otherwise%",
--- End diff --
This is an interesting idea, but I think the right primitive to implement
here is `ifelse` [1], which will capture both the if and the else clause in the
same function.
So I think we can remove the `%otherwise%` operator for now and we can
implement `ifelse` in a different PR if its too complicated to include in this
one.
[1] http://www.inside-r.org/r-doc/base/ifelse
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