[SPARKR-92] Phase 2: implement sum(rdd)

R/pkg/NAMESPACE

@@ -57,6 +57,7 @@ exportMethods(
               "saveAsObjectFile",
               "sortBy",
               "sortByKey",
+              "sumRDD",
               "take",
               "takeOrdered",
               "takeSample",

R/pkg/R/RDD.R

@@ -660,6 +660,23 @@ setMethod("minimum",
             reduce(x, min)
           })
 
+#' Add up the elements in an RDD.
+#'
+#' @param x The RDD to add up the elements in
+#' @examples
+#'\dontrun{
+#' sc <- sparkR.init()
+#' rdd <- parallelize(sc, 1:10)
+#' sumRDD(rdd) # 55
+#'}
+#' @rdname sumRDD 
+#' @aliases sumRDD,RDD
+setMethod("sumRDD",
+          signature(x = "RDD"),
+          function(x) {
+            reduce(x, "+")
+          })
+
 #' Applies a function to all elements in an RDD, and force evaluation.
 #'
 #' @param x The RDD to apply the function

R/pkg/R/generics.R

@@ -130,6 +130,10 @@ setGeneric("maximum", function(x) { standardGeneric("maximum") })
 #' @export
 setGeneric("minimum", function(x) { standardGeneric("minimum") })
 
+#' @rdname sumRDD 
+#' @export
+setGeneric("sumRDD", function(x) { standardGeneric("sumRDD") })
+
 #' @rdname name
 #' @export
 setGeneric("name", function(x) { standardGeneric("name") })

R/pkg/inst/tests/test_rdd.R

@@ -286,6 +286,11 @@ test_that("minimum() on RDDs", {
   expect_equal(min, 1)
 })
 
+test_that("sumRDD() on RDDs", {
+  sum <- sumRDD(rdd)
+  expect_equal(sum, 55)
+})
+
 test_that("keyBy on RDDs", {
   func <- function(x) { x*x }
   keys <- keyBy(rdd, func)