Added examples for statistical summarization:

* Scala: StatisticalSummary.scala
** Tests: correlation, MultivariateOnlineSummarizer
* python: statistical_summary.py
** Tests: correlation (since MultivariateOnlineSummarizer has no Python API)

Added sc.stop() to all examples.

CorrelationSuite.scala
* Added 1 test for RDDs with only 1 value

Python SparseVector (pyspark/mllib/linalg.py)
* Added toDense() function

python/run-tests script
* Added stat.py (doc test)

examples/src/main/python/als.py

@@ -97,3 +97,5 @@ def update(i, vec, mat, ratings):
         error = rmse(R, ms, us)
         print "Iteration %d:" % i
         print "\nRMSE: %5.4f\n" % error
+
+    sc.stop()

examples/src/main/python/cassandra_inputformat.py

@@ -77,3 +77,5 @@
     output = cass_rdd.collect()
     for (k, v) in output:
         print (k, v)
+
+    sc.stop()

examples/src/main/python/cassandra_outputformat.py

@@ -81,3 +81,5 @@
         conf=conf,
         keyConverter="org.apache.spark.examples.pythonconverters.ToCassandraCQLKeyConverter",
         valueConverter="org.apache.spark.examples.pythonconverters.ToCassandraCQLValueConverter")
+
+    sc.stop()

examples/src/main/python/hbase_inputformat.py

@@ -71,3 +71,5 @@
     output = hbase_rdd.collect()
     for (k, v) in output:
         print (k, v)
+
+    sc.stop()

examples/src/main/python/hbase_outputformat.py

@@ -63,3 +63,5 @@
         conf=conf,
         keyConverter="org.apache.spark.examples.pythonconverters.StringToImmutableBytesWritableConverter",
         valueConverter="org.apache.spark.examples.pythonconverters.StringListToPutConverter")
+
+    sc.stop()

examples/src/main/python/kmeans.py

@@ -77,3 +77,5 @@ def closestPoint(p, centers):
             kPoints[x] = y
 
     print "Final centers: " + str(kPoints)
+
+    sc.stop()

examples/src/main/python/logistic_regression.py

@@ -80,3 +80,5 @@ def add(x, y):
         w -= points.map(lambda m: gradient(m, w)).reduce(add)
 
     print "Final w: " + str(w)
+
+    sc.stop()

examples/src/main/python/mllib/decision_tree_runner.py

@@ -17,6 +17,8 @@
 
 """
 Decision tree classification and regression using MLlib.
+
+This example requires NumPy (http://www.numpy.org/).
 """
 
 import numpy, os, sys
@@ -117,6 +119,7 @@ def usage():
     if len(sys.argv) == 2:
         dataPath = sys.argv[1]
     if not os.path.isfile(dataPath):
+        sc.stop()
         usage()
     points = MLUtils.loadLibSVMFile(sc, dataPath)
 
@@ -131,3 +134,5 @@ def usage():
     print "  Model depth: %d\n" % model.depth()
     print "  Training accuracy: %g\n" % getAccuracy(model, reindexedData)
     print model
+
+    sc.stop()

examples/src/main/python/mllib/kmeans.py

@@ -42,3 +42,4 @@ def parseVector(line):
     k = int(sys.argv[2])
     model = KMeans.train(data, k)
     print "Final centers: " + str(model.clusterCenters)
+    sc.stop()

examples/src/main/python/mllib/logistic_regression.py

@@ -50,3 +50,4 @@ def parsePoint(line):
     model = LogisticRegressionWithSGD.train(points, iterations)
     print "Final weights: " + str(model.weights)
     print "Final intercept: " + str(model.intercept)
+    sc.stop()

examples/src/main/python/mllib/statistical_summary.py

@@ -0,0 +1,60 @@
+#
+# 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.
+#
+
+"""
+Statistical summarization using MLlib.
+"""
+
+import sys
+
+from pyspark import SparkContext
+from pyspark.mllib.regression import LabeledPoint
+from pyspark.mllib.stat import Statistics
+from pyspark.mllib.util import MLUtils
+
+
+if __name__ == "__main__":
+    if len(sys.argv) not in [1,2]:
+        print >> sys.stderr, "Usage: statistical_summary (<file>)"
+        exit(-1)
+    sc = SparkContext(appName="PythonStatisticalSummary")
+    if len(sys.argv) == 2:
+        filepath = sys.argv[1]
+    else:
+        filepath = 'data/mllib/sample_linear_regression_data.txt'
+    corrType = 'pearson'
+
+    points = MLUtils.loadLibSVMFile(sc, filepath)\
+        .map(lambda lp: LabeledPoint(lp.label, lp.features.toDense()))
+
+    print ''
+    print 'Summary of data file: ' + filepath
+    print '%d data points' % points.count()
+
+    # Statistics (correlations)
+    print ''
+    print 'Correlation (%s) between label and each feature' % corrType
+    print 'Feature\tCorrelation'
+    numFeatures = points.take(1)[0].features.size
+    labelRDD = points.map(lambda lp: lp.label)
+    for i in range(numFeatures):
+        featureRDD = points.map(lambda lp: lp.features[i])
+        corr = Statistics.corr(labelRDD, featureRDD, corrType)
+        print '%d\t%g' % (i, corr)
+    print ''
+
+    sc.stop()

examples/src/main/python/pagerank.py

@@ -68,3 +68,5 @@ def parseNeighbors(urls):
     # Collects all URL ranks and dump them to console.
     for (link, rank) in ranks.collect():
         print "%s has rank: %s." % (link, rank)
+
+    sc.stop()

examples/src/main/python/pi.py

@@ -37,3 +37,5 @@ def f(_):
 
     count = sc.parallelize(xrange(1, n+1), slices).map(f).reduce(add)
     print "Pi is roughly %f" % (4.0 * count / n)
+
+    sc.stop()

examples/src/main/python/sort.py

@@ -34,3 +34,5 @@
     output = sortedCount.collect()
     for (num, unitcount) in output:
         print num
+
+    sc.stop()

examples/src/main/python/transitive_closure.py

@@ -64,3 +64,5 @@ def generateGraph():
             break
 
     print "TC has %i edges" % tc.count()
+
+    sc.stop()

examples/src/main/python/wordcount.py

@@ -33,3 +33,5 @@
     output = counts.collect()
     for (word, count) in output:
         print "%s: %i" % (word, count)
+
+    sc.stop()

examples/src/main/scala/org/apache/spark/examples/mllib/StatisticalSummary.scala

@@ -0,0 +1,121 @@
+/*
+ * 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.
+ */
+
+package org.apache.spark.examples.mllib
+
+import org.apache.spark.mllib.regression.LabeledPoint
+import org.apache.spark.rdd.RDD
+import scopt.OptionParser
+
+import org.apache.spark.mllib.linalg.Vectors
+import org.apache.spark.mllib.stat.{MultivariateOnlineSummarizer, Statistics}
+import org.apache.spark.mllib.util.MLUtils
+import org.apache.spark.{SparkConf, SparkContext}
+
+
+/**
+ * An example app for summarizing multivariate data from a file. Run with
+ * {{{
+ * bin/run-example org.apache.spark.examples.mllib.Statistics
+ * }}}
+ * By default, this loads a synthetic dataset from `data/mllib/sample_linear_regression_data.txt`.
+ * If you use it as a template to create your own app, please use `spark-submit` to submit your app.
+ */
+object StatisticalSummary extends App {
+
+  case class Params(input: String = "data/mllib/sample_linear_regression_data.txt")
+
+  val defaultParams = Params()
+
+  val parser = new OptionParser[Params]("StatisticalSummary") {
+    head("StatisticalSummary: an example app for MultivariateOnlineSummarizer and Statistics (correlation)")
+    opt[String]("input")
+      .text(s"Input paths to labeled examples in LIBSVM format, default: ${defaultParams.input}")
+      .action((x, c) => c.copy(input = x))
+    note(
+      """
+        |For example, the following command runs this app on a synthetic dataset:
+        |
+        | bin/spark-submit --class org.apache.spark.examples.mllib.StatisticalSummary \
+        |  examples/target/scala-*/spark-examples-*.jar \
+        |  data/mllib/sample_linear_regression_data.txt
+      """.stripMargin)
+  }
+
+  parser.parse(args, defaultParams).map { params =>
+    run(params)
+  } getOrElse {
+    sys.exit(1)
+  }
+
+  def runStatisticalSummary(examples: RDD[LabeledPoint], params: Params) {
+    // Summarize labels
+    val labelSummary = examples.aggregate(new MultivariateOnlineSummarizer())(
+      (summary, lp) => summary.add(Vectors.dense(lp.label)),
+      (sum1, sum2) => sum1.merge(sum2))
+
+    // Summarize features
+    val featureSummary = examples.aggregate(new MultivariateOnlineSummarizer())(
+      (summary, lp) => summary.add(lp.features),
+      (sum1, sum2) => sum1.merge(sum2))
+
+    println()
+    println(s"Summary statistics")
+    println(s"\tLabel\tFeatures")
+    println(s"mean\t${labelSummary.mean(0)}\t${featureSummary.mean.toArray.mkString("\t")}")
+    println(s"var\t${labelSummary.variance(0)}\t${featureSummary.variance.toArray.mkString("\t")}")
+    println(
+      s"nnz\t${labelSummary.numNonzeros(0)}\t${featureSummary.numNonzeros.toArray.mkString("\t")}")
+    println(s"max\t${labelSummary.max(0)}\t${featureSummary.max.toArray.mkString("\t")}")
+    println(s"min\t${labelSummary.min(0)}\t${featureSummary.min.toArray.mkString("\t")}")
+    println()
+  }
+
+  def runCorrelations(examples: RDD[LabeledPoint], params: Params) {
+    // Calculate label -- feature correlations
+    val labelRDD = examples.map(_.label)
+    val numFeatures = examples.take(1)(0).features.size
+    val corrType = "pearson"
+    println()
+    println(s"Correlation ($corrType) between label and each feature")
+    println(s"Feature\tCorrelation")
+    var feature = 0
+    while (feature < numFeatures) {
+      val featureRDD = examples.map(_.features(feature))
+      val corr = Statistics.corr(labelRDD, featureRDD)
+      println(s"$feature\t$corr")
+      feature += 1
+    }
+    println()
+  }
+
+  def run(params: Params) {
+    val conf = new SparkConf().setAppName(s"StatisticalSummary with $params")
+    val sc = new SparkContext(conf)
+
+    val examples = MLUtils.loadLibSVMFile(sc, params.input).cache()
+
+    println(s"Summary of data file: ${params.input}")
+    println(s"${examples.count} data points")
+
+    runStatisticalSummary(examples, params)
+
+    runCorrelations(examples, params)
+
+    sc.stop()
+  }
+}

mllib/src/main/scala/org/apache/spark/mllib/stat/MultivariateOnlineSummarizer.scala

@@ -55,8 +55,8 @@ class MultivariateOnlineSummarizer extends MultivariateStatisticalSummary with S
    */
   def add(sample: Vector): this.type = {
     if (n == 0) {
-      require(sample.toBreeze.length > 0, s"Vector should have dimension larger than zero.")
-      n = sample.toBreeze.length
+      require(sample.size > 0, s"Vector should have dimension larger than zero.")
+      n = sample.size
 
       currMean = BDV.zeros[Double](n)
       currM2n = BDV.zeros[Double](n)
@@ -65,8 +65,8 @@ class MultivariateOnlineSummarizer extends MultivariateStatisticalSummary with S
       currMin = BDV.fill(n)(Double.MaxValue)
     }
 
-    require(n == sample.toBreeze.length, s"Dimensions mismatch when adding new sample." +
-      s" Expecting $n but got ${sample.toBreeze.length}.")
+    require(n == sample.size, s"Dimensions mismatch when adding new sample." +
+      s" Expecting $n but got ${sample.size}.")
 
     sample.toBreeze.activeIterator.foreach {
       case (_, 0.0) => // Skip explicit zero elements.

mllib/src/test/scala/org/apache/spark/mllib/stat/CorrelationSuite.scala

@@ -39,6 +39,13 @@ class CorrelationSuite extends FunSuite with LocalSparkContext {
     Vectors.dense(9.0, 0.0, 0.0, 1.0)
   )
 
+  test("corr(x, y) pearson, 1 value in data") {
+    val x = sc.parallelize(Array(1.0))
+    val y = sc.parallelize(Array(4.0))
+    assert(Statistics.corr(x, y, "pearson").isNaN)
+    assert(Statistics.corr(x, y, "spearman").isNaN)
+  }
+
   test("corr(x, y) default, pearson") {
     val x = sc.parallelize(xData)
     val y = sc.parallelize(yData)
@@ -58,7 +65,7 @@ class CorrelationSuite extends FunSuite with LocalSparkContext {
 
     // RDD of zero variance
     val z = sc.parallelize(zeros)
-    assert(Statistics.corr(x, z).isNaN())
+    assert(Statistics.corr(x, z).isNaN)
   }
 
   test("corr(x, y) spearman") {
@@ -78,7 +85,7 @@ class CorrelationSuite extends FunSuite with LocalSparkContext {
 
     // RDD of zero variance => zero variance in ranks
     val z = sc.parallelize(zeros)
-    assert(Statistics.corr(x, z, "spearman").isNaN())
+    assert(Statistics.corr(x, z, "spearman").isNaN)
   }
 
   test("corr(X) default, pearson") {

mllib/src/test/scala/org/apache/spark/mllib/stat/MultivariateOnlineSummarizerSuite.scala

@@ -139,7 +139,8 @@ class MultivariateOnlineSummarizerSuite extends FunSuite {
     assert(summarizer.numNonzeros ~== Vectors.dense(3, 5, 2) absTol 1E-5, "numNonzeros mismatch")
 
     assert(summarizer.variance ~==
-      Vectors.dense(3.857666666666, 7.0456666666666, 2.48166666666666) absTol 1E-5, "variance mismatch")
+      Vectors.dense(3.857666666666, 7.0456666666666, 2.48166666666666) absTol 1E-5,
+      "variance mismatch")
 
     assert(summarizer.count === 6)
   }
@@ -167,7 +168,8 @@ class MultivariateOnlineSummarizerSuite extends FunSuite {
     assert(summarizer.numNonzeros ~== Vectors.dense(3, 5, 2) absTol 1E-5, "numNonzeros mismatch")
 
     assert(summarizer.variance ~==
-      Vectors.dense(3.857666666666, 7.0456666666666, 2.48166666666666) absTol 1E-5, "variance mismatch")
+      Vectors.dense(3.857666666666, 7.0456666666666, 2.48166666666666) absTol 1E-5,
+      "variance mismatch")
 
     assert(summarizer.count === 6)
   }

python/pyspark/mllib/linalg.py

@@ -23,6 +23,7 @@
 SciPy is available in their environment.
 """
 
+import numpy
 from numpy import array, array_equal, ndarray, float64, int32
 
 
@@ -160,6 +161,15 @@ def squared_distance(self, other):
                 j += 1
             return result
 
+    def toDense(self):
+        """
+        Returns a copy of this SparseVector as a 1-dimensional NumPy array.
+        """
+        arr = numpy.zeros(self.size)
+        for i in range(self.indices.size):
+            arr[self.indices[i]] = self.values[i]
+        return arr
+
     def __str__(self):
         inds = "[" + ",".join([str(i) for i in self.indices]) + "]"
         vals = "[" + ",".join([str(v) for v in self.values]) + "]"

python/run-tests

@@ -70,6 +70,7 @@ run_test "pyspark/mllib/linalg.py"
 run_test "pyspark/mllib/random.py"
 run_test "pyspark/mllib/recommendation.py"
 run_test "pyspark/mllib/regression.py"
+run_test "pyspark/mllib/stat.py"
 run_test "pyspark/mllib/tests.py"
 run_test "pyspark/mllib/util.py"