[SPARK-7242] added python api for freqItems in DataFrames

The python api for DataFrame's plus addressed your comments from previous PR.
rxin

Author: Burak Yavuz <brkyvz@gmail.com>

Closes #5859 from brkyvz/df-freq-py2 and squashes the following commits:

f9aa9ce [Burak Yavuz] addressed comments v0.1
4b25056 [Burak Yavuz] added python api for freqItems

1 files changed, 6 insertions, 3 deletions

diff --git a/sql/core/src/main/scala/org/apache/spark/sql/DataFrameStatFunctions.scala b/sql/core/src/main/scala/org/apache/spark/sql/DataFrameStatFunctions.scala
index 23652aeb7c..e8fa829477 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/DataFrameStatFunctions.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/DataFrameStatFunctions.scala
@@ -43,7 +43,10 @@ final class DataFrameStatFunctions private[sql](df: DataFrame) {
   }
 
   /**
-   * Runs `freqItems` with a default `support` of 1%.
+   * Finding frequent items for columns, possibly with false positives. Using the
+   * frequent element count algorithm described in
+   * [[http://dx.doi.org/10.1145/762471.762473, proposed by Karp, Schenker, and Papadimitriou]].
+   * Uses a `default` support of 1%.
    *
    * @param cols the names of the columns to search frequent items in.
    * @return A Local DataFrame with the Array of frequent items for each column.
@@ -55,14 +58,14 @@ final class DataFrameStatFunctions private[sql](df: DataFrame) {
   /**
    * Python friendly implementation for `freqItems`
    */
-  def freqItems(cols: List[String], support: Double): DataFrame = {
+  def freqItems(cols: Seq[String], support: Double): DataFrame = {
     FrequentItems.singlePassFreqItems(df, cols, support)
   }
 
   /**
    * Python friendly implementation for `freqItems` with a default `support` of 1%.
    */
-  def freqItems(cols: List[String]): DataFrame = {
+  def freqItems(cols: Seq[String]): DataFrame = {
     FrequentItems.singlePassFreqItems(df, cols, 0.01)
   }