[SPARK-11978][ML] Move dataset_example.py to examples/ml and rename to dataframe_example.py

Since ```Dataset``` has a new meaning in Spark 1.6, we should rename it to avoid confusion.
#9873 finished the work of Scala example, here we focus on the Python one.
Move dataset_example.py to ```examples/ml``` and rename to ```dataframe_example.py```.
BTW, fix minor missing issues of #9873.
cc mengxr

Author: Yanbo Liang <ybliang8@gmail.com>

Closes #9957 from yanboliang/SPARK-11978.

1 files changed, 75 insertions, 0 deletions

diff --git a/examples/src/main/python/ml/dataframe_example.py b/examples/src/main/python/ml/dataframe_example.py
new file mode 100644
index 0000000000..d2644ca335
--- /dev/null
+++ b/examples/src/main/python/ml/dataframe_example.py
@@ -0,0 +1,75 @@
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You under the Apache License, Version 2.0
+# (the "License"); you may not use this file except in compliance with
+# the License.  You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+"""
+An example of how to use DataFrame for ML. Run with::
+    bin/spark-submit examples/src/main/python/ml/dataframe_example.py <input>
+"""
+from __future__ import print_function
+
+import os
+import sys
+import tempfile
+import shutil
+
+from pyspark import SparkContext
+from pyspark.sql import SQLContext
+from pyspark.mllib.stat import Statistics
+
+if __name__ == "__main__":
+    if len(sys.argv) > 2:
+        print("Usage: dataframe_example.py <libsvm file>", file=sys.stderr)
+        exit(-1)
+    sc = SparkContext(appName="DataFrameExample")
+    sqlContext = SQLContext(sc)
+    if len(sys.argv) == 2:
+        input = sys.argv[1]
+    else:
+        input = "data/mllib/sample_libsvm_data.txt"
+
+    # Load input data
+    print("Loading LIBSVM file with UDT from " + input + ".")
+    df = sqlContext.read.format("libsvm").load(input).cache()
+    print("Schema from LIBSVM:")
+    df.printSchema()
+    print("Loaded training data as a DataFrame with " +
+          str(df.count()) + " records.")
+
+    # Show statistical summary of labels.
+    labelSummary = df.describe("label")
+    labelSummary.show()
+
+    # Convert features column to an RDD of vectors.
+    features = df.select("features").map(lambda r: r.features)
+    summary = Statistics.colStats(features)
+    print("Selected features column with average values:\n" +
+          str(summary.mean()))
+
+    # Save the records in a parquet file.
+    tempdir = tempfile.NamedTemporaryFile(delete=False).name
+    os.unlink(tempdir)
+    print("Saving to " + tempdir + " as Parquet file.")
+    df.write.parquet(tempdir)
+
+    # Load the records back.
+    print("Loading Parquet file with UDT from " + tempdir)
+    newDF = sqlContext.read.parquet(tempdir)
+    print("Schema from Parquet:")
+    newDF.printSchema()
+    shutil.rmtree(tempdir)
+
+    sc.stop()