[SPARK-9324] [SPARK-9322] [SPARK-9321] [SPARKR] Some aliases for R-like functions in DataFrames

Adds following aliases:
* unique (distinct)
* rbind (unionAll): accepts many DataFrames
* nrow (count)
* ncol
* dim
* names (columns): along with the replacement function to change names

Author: Hossein <hossein@databricks.com>

Closes #7764 from falaki/sparkR-alias and squashes the following commits:

56016f5 [Hossein] Updated R documentation
5e4a4d0 [Hossein] Removed extra code
f51cbef [Hossein] Merge branch 'master' into sparkR-alias
c1b88bd [Hossein] Moved setGeneric and other comments applied
d9307f8 [Hossein] Added tests
b5aa988 [Hossein] Added dim, ncol, nrow, names, rbind, and unique functions to DataFrames

4 files changed, 119 insertions, 3 deletions

diff --git a/R/pkg/NAMESPACE b/R/pkg/NAMESPACE
index a329e14f25..ff116cb1fb 100644
--- a/R/pkg/NAMESPACE
+++ b/R/pkg/NAMESPACE
@@ -29,6 +29,7 @@ exportMethods("arrange",
               "count",
               "crosstab",
               "describe",
+              "dim",
               "distinct",
               "dropna",
               "dtypes",
@@ -45,11 +46,15 @@ exportMethods("arrange",
               "isLocal",
               "join",
               "limit",
+              "names",
+              "ncol",
+              "nrow",
               "orderBy",
               "mutate",
               "names",
               "persist",
               "printSchema",
+              "rbind",
               "registerTempTable",
               "rename",
               "repartition",
@@ -66,6 +71,7 @@ exportMethods("arrange",
               "summarize",
               "take",
               "unionAll",
+              "unique",
               "unpersist",
               "where",
               "withColumn",
diff --git a/R/pkg/R/DataFrame.R b/R/pkg/R/DataFrame.R
index b31ad3729e..b4065d2944 100644
--- a/R/pkg/R/DataFrame.R
+++ b/R/pkg/R/DataFrame.R
@@ -255,6 +255,16 @@ setMethod("names",
             columns(x)
           })
 
+#' @rdname columns
+setMethod("names<-",
+          signature(x = "DataFrame"),
+          function(x, value) {
+            if (!is.null(value)) {
+              sdf <- callJMethod(x@sdf, "toDF", listToSeq(as.list(value)))
+              dataFrame(sdf)
+            }
+          })
+
 #' Register Temporary Table
 #'
 #' Registers a DataFrame as a Temporary Table in the SQLContext
@@ -473,6 +483,18 @@ setMethod("distinct",
             dataFrame(sdf)
           })
 
+#' @title Distinct rows in a DataFrame
+#
+#' @description Returns a new DataFrame containing distinct rows in this DataFrame
+#'
+#' @rdname unique
+#' @aliases unique
+setMethod("unique",
+          signature(x = "DataFrame"),
+          function(x) {
+            distinct(x)
+          })
+
 #' Sample
 #'
 #' Return a sampled subset of this DataFrame using a random seed.
@@ -534,6 +556,58 @@ setMethod("count",
             callJMethod(x@sdf, "count")
           })
 
+#' @title Number of rows for a DataFrame
+#' @description Returns number of rows in a DataFrames
+#'
+#' @name nrow
+#'
+#' @rdname nrow
+#' @aliases count
+setMethod("nrow",
+          signature(x = "DataFrame"),
+          function(x) {
+            count(x)
+          })
+
+#' Returns the number of columns in a DataFrame
+#'
+#' @param x a SparkSQL DataFrame
+#'
+#' @rdname ncol
+#' @export
+#' @examples
+#'\dontrun{
+#' sc <- sparkR.init()
+#' sqlContext <- sparkRSQL.init(sc)
+#' path <- "path/to/file.json"
+#' df <- jsonFile(sqlContext, path)
+#' ncol(df)
+#' }
+setMethod("ncol",
+          signature(x = "DataFrame"),
+          function(x) {
+            length(columns(x))
+          })
+
+#' Returns the dimentions (number of rows and columns) of a DataFrame
+#' @param x a SparkSQL DataFrame
+#'
+#' @rdname dim
+#' @export
+#' @examples
+#'\dontrun{
+#' sc <- sparkR.init()
+#' sqlContext <- sparkRSQL.init(sc)
+#' path <- "path/to/file.json"
+#' df <- jsonFile(sqlContext, path)
+#' dim(df)
+#' }
+setMethod("dim",
+          signature(x = "DataFrame"),
+          function(x) {
+            c(count(x), ncol(x))
+          })
+
 #' Collects all the elements of a Spark DataFrame and coerces them into an R data.frame.
 #'
 #' @param x A SparkSQL DataFrame
@@ -1231,6 +1305,22 @@ setMethod("unionAll",
             dataFrame(unioned)
           })
 
+#' @title Union two or more DataFrames
+#
+#' @description Returns a new DataFrame containing rows of all parameters.
+#
+#' @rdname rbind
+#' @aliases unionAll
+setMethod("rbind",
+          signature(... = "DataFrame"),
+          function(x, ..., deparse.level = 1) {
+            if (nargs() == 3) {
+              unionAll(x, ...)
+            } else {
+              unionAll(x, Recall(..., deparse.level = 1))
+            }
+          })
+
 #' Intersect
 #'
 #' Return a new DataFrame containing rows only in both this DataFrame
diff --git a/R/pkg/R/generics.R b/R/pkg/R/generics.R
index a3a121058e..71d1e348c4 100644
--- a/R/pkg/R/generics.R
+++ b/R/pkg/R/generics.R
@@ -669,3 +669,7 @@ setGeneric("upper", function(x) { standardGeneric("upper") })
 #' @rdname glm
 #' @export
 setGeneric("glm")
+
+#' @rdname rbind
+#' @export
+setGeneric("rbind", signature = "...")
diff --git a/R/pkg/inst/tests/test_sparkSQL.R b/R/pkg/inst/tests/test_sparkSQL.R
index 25f697314f..9faee8d59c 100644
--- a/R/pkg/inst/tests/test_sparkSQL.R
+++ b/R/pkg/inst/tests/test_sparkSQL.R
@@ -88,6 +88,9 @@ test_that("create DataFrame from RDD", {
   df <- createDataFrame(sqlContext, rdd, list("a", "b"))
   expect_is(df, "DataFrame")
   expect_equal(count(df), 10)
+  expect_equal(nrow(df), 10)
+  expect_equal(ncol(df), 2)
+  expect_equal(dim(df), c(10, 2))
   expect_equal(columns(df), c("a", "b"))
   expect_equal(dtypes(df), list(c("a", "int"), c("b", "string")))
 
@@ -491,7 +494,7 @@ test_that("head() and first() return the correct data", {
   expect_equal(nrow(testFirst), 1)
 })
 
-test_that("distinct() on DataFrames", {
+test_that("distinct() and unique on DataFrames", {
   lines <- c("{\"name\":\"Michael\"}",
              "{\"name\":\"Andy\", \"age\":30}",
              "{\"name\":\"Justin\", \"age\":19}",
@@ -503,6 +506,10 @@ test_that("distinct() on DataFrames", {
   uniques <- distinct(df)
   expect_is(uniques, "DataFrame")
   expect_equal(count(uniques), 3)
+
+  uniques2 <- unique(df)
+  expect_is(uniques2, "DataFrame")
+  expect_equal(count(uniques2), 3)
 })
 
 test_that("sample on a DataFrame", {
@@ -815,7 +822,7 @@ test_that("isLocal()", {
   expect_false(isLocal(df))
 })
 
-test_that("unionAll(), except(), and intersect() on a DataFrame", {
+test_that("unionAll(), rbind(), except(), and intersect() on a DataFrame", {
   df <- jsonFile(sqlContext, jsonPath)
 
   lines <- c("{\"name\":\"Bob\", \"age\":24}",
@@ -830,6 +837,11 @@ test_that("unionAll(), except(), and intersect() on a DataFrame", {
   expect_equal(count(unioned), 6)
   expect_equal(first(unioned)$name, "Michael")
 
+  unioned2 <- arrange(rbind(unioned, df, df2), df$age)
+  expect_is(unioned2, "DataFrame")
+  expect_equal(count(unioned2), 12)
+  expect_equal(first(unioned2)$name, "Michael")
+
   excepted <- arrange(except(df, df2), desc(df$age))
   expect_is(unioned, "DataFrame")
   expect_equal(count(excepted), 2)
@@ -853,7 +865,7 @@ test_that("withColumn() and withColumnRenamed()", {
   expect_equal(columns(newDF2)[1], "newerAge")
 })
 
-test_that("mutate() and rename()", {
+test_that("mutate(), rename() and names()", {
   df <- jsonFile(sqlContext, jsonPath)
   newDF <- mutate(df, newAge = df$age + 2)
   expect_equal(length(columns(newDF)), 3)
@@ -863,6 +875,10 @@ test_that("mutate() and rename()", {
   newDF2 <- rename(df, newerAge = df$age)
   expect_equal(length(columns(newDF2)), 2)
   expect_equal(columns(newDF2)[1], "newerAge")
+
+  names(newDF2) <- c("newerName", "evenNewerAge")
+  expect_equal(length(names(newDF2)), 2)
+  expect_equal(names(newDF2)[1], "newerName")
 })
 
 test_that("write.df() on DataFrame and works with parquetFile", {