[SPARK-10807] [SPARKR] Added as.data.frame as a synonym for collect

Created method as.data.frame as a synonym for collect().

Author: Oscar D. Lara Yejas <olarayej@mail.usf.edu>
Author: olarayej <oscar.lara.yejas@us.ibm.com>
Author: Oscar D. Lara Yejas <oscar.lara.yejas@us.ibm.com>

Closes #8908 from olarayej/SPARK-10807.

1 files changed, 25 insertions, 0 deletions

diff --git a/R/pkg/R/DataFrame.R b/R/pkg/R/DataFrame.R
index c3c1893487..65e368c47d 100644
--- a/R/pkg/R/DataFrame.R
+++ b/R/pkg/R/DataFrame.R
@@ -1848,3 +1848,28 @@ setMethod("crosstab",
             sct <- callJMethod(statFunctions, "crosstab", col1, col2)
             collect(dataFrame(sct))
           })
+
+
+#' This function downloads the contents of a DataFrame into an R's data.frame.
+#' Since data.frames are held in memory, ensure that you have enough memory
+#' in your system to accommodate the contents.
+#' 
+#' @title Download data from a DataFrame into a data.frame
+#' @param x a DataFrame
+#' @return a data.frame
+#' @rdname as.data.frame
+#' @examples \dontrun{
+#' 
+#' irisDF <- createDataFrame(sqlContext, iris)
+#' df <- as.data.frame(irisDF[irisDF$Species == "setosa", ])
+#' }
+setMethod("as.data.frame",
+          signature(x = "DataFrame"),
+          function(x, ...) {
+            # Check if additional parameters have been passed
+            if (length(list(...)) > 0) {
+              stop(paste("Unused argument(s): ", paste(list(...), collapse=", ")))
+            }
+            collect(x)
+          }
+)