[SPARK-14639][PYTHON][R] Add bround function in Python/R.

R/pkg/NAMESPACE

@@ -125,6 +125,7 @@ exportMethods("%in%",
               "between",
               "bin",
               "bitwiseNOT",
+              "bround",
               "cast",
               "cbrt",
               "ceil",

R/pkg/R/functions.R

@@ -994,7 +994,7 @@ setMethod("rint",
 
 #' round
 #'
-#' Returns the value of the column `e` rounded to 0 decimal places.
+#' Returns the value of the column `e` rounded to 0 decimal places using HALF_UP rounding mode.
 #'
 #' @rdname round
 #' @name round
@@ -1008,6 +1008,26 @@ setMethod("round",
             column(jc)
           })
 
+#' bround
+#'
+#' Returns the value of the column `e` rounded to `scale` decimal places using HALF_EVEN rounding
+#' mode if `scale` >= 0 or at integral part when `scale` < 0.
+#' Also known as Gaussian rounding or bankers' rounding that rounds to the nearest even number.
+#' bround(2.5, 0) = 2, bround(3.5, 0) = 4.
+#'
+#' @rdname bround
+#' @name bround
+#' @family math_funcs
+#' @export
+#' @examples \dontrun{bround(df$c, 0)}
+setMethod("bround",
+          signature(x = "Column"),
+          function(x, scale = 0) {
+            jc <- callJStatic("org.apache.spark.sql.functions", "bround", x@jc, as.integer(scale))
+            column(jc)
+          })
+
+
 #' rtrim
 #'
 #' Trim the spaces from right end for the specified string value.

R/pkg/R/generics.R

@@ -751,6 +751,10 @@ setGeneric("bin", function(x) { standardGeneric("bin") })
 #' @export
 setGeneric("bitwiseNOT", function(x) { standardGeneric("bitwiseNOT") })
 
+#' @rdname bround
+#' @export
+setGeneric("bround", function(x, ...) { standardGeneric("bround") })
+
 #' @rdname cbrt
 #' @export
 setGeneric("cbrt", function(x) { standardGeneric("cbrt") })

R/pkg/inst/tests/testthat/test_sparkSQL.R

@@ -1087,6 +1087,11 @@ test_that("column functions", {
   expect_equal(collect(select(df, last(df$age, TRUE)))[[1]], 19)
   expect_equal(collect(select(df, last("age")))[[1]], 19)
   expect_equal(collect(select(df, last("age", TRUE)))[[1]], 19)
+
+  # Test bround()
+  df <- createDataFrame(sqlContext, data.frame(x = c(2.5, 3.5)))
+  expect_equal(collect(select(df, bround(df$x, 0)))[[1]][1], 2)
+  expect_equal(collect(select(df, bround(df$x, 0)))[[1]][2], 4)
 })
 
 test_that("column binary mathfunctions", {

python/pyspark/sql/functions.py

@@ -467,16 +467,29 @@ def randn(seed=None):
 @since(1.5)
 def round(col, scale=0):
     """
-    Round the value of `e` to `scale` decimal places if `scale` >= 0
+    Round the given value to `scale` decimal places using HALF_UP rounding mode if `scale` >= 0
     or at integral part when `scale` < 0.
 
-    >>> sqlContext.createDataFrame([(2.546,)], ['a']).select(round('a', 1).alias('r')).collect()
-    [Row(r=2.5)]
+    >>> sqlContext.createDataFrame([(2.5,)], ['a']).select(round('a', 0).alias('r')).collect()
+    [Row(r=3.0)]
     """
     sc = SparkContext._active_spark_context
     return Column(sc._jvm.functions.round(_to_java_column(col), scale))
 
 
+@since(2.0)
+def bround(col, scale=0):
+    """
+    Round the given value to `scale` decimal places using HALF_EVEN rounding mode if `scale` >= 0
+    or at integral part when `scale` < 0.
+
+    >>> sqlContext.createDataFrame([(2.5,)], ['a']).select(bround('a', 0).alias('r')).collect()
+    [Row(r=2.0)]
+    """
+    sc = SparkContext._active_spark_context
+    return Column(sc._jvm.functions.bround(_to_java_column(col), scale))
+
+
 @since(1.5)
 def shiftLeft(col, numBits):
     """Shift the given value numBits left.