[SPARK-15141][EXAMPLE][DOC] Update OneVsRest Examples

## What changes were proposed in this pull request?
1, Add python example for OneVsRest
2, remove args-parsing

## How was this patch tested?
manual tests
`./bin/spark-submit examples/src/main/python/ml/one_vs_rest_example.py`

Author: Zheng RuiFeng <ruifengz@foxmail.com>

Closes #12920 from zhengruifeng/ovr_pe.

1 files changed, 30 insertions, 184 deletions

diff --git a/examples/src/main/java/org/apache/spark/examples/ml/JavaOneVsRestExample.java b/examples/src/main/java/org/apache/spark/examples/ml/JavaOneVsRestExample.java
index e0cb752224..5bf455ebfe 100644
--- a/examples/src/main/java/org/apache/spark/examples/ml/JavaOneVsRestExample.java
+++ b/examples/src/main/java/org/apache/spark/examples/ml/JavaOneVsRestExample.java
@@ -17,222 +17,68 @@
 
 package org.apache.spark.examples.ml;
 
-import org.apache.commons.cli.*;
-
 // $example on$
 import org.apache.spark.ml.classification.LogisticRegression;
 import org.apache.spark.ml.classification.OneVsRest;
 import org.apache.spark.ml.classification.OneVsRestModel;
-import org.apache.spark.ml.util.MetadataUtils;
-import org.apache.spark.mllib.evaluation.MulticlassMetrics;
-import org.apache.spark.mllib.linalg.Matrix;
-import org.apache.spark.mllib.linalg.Vector;
+import org.apache.spark.ml.evaluation.MulticlassClassificationEvaluator;
 import org.apache.spark.sql.Dataset;
 import org.apache.spark.sql.Row;
-import org.apache.spark.sql.SparkSession;
-import org.apache.spark.sql.types.StructField;
 // $example off$
+import org.apache.spark.sql.SparkSession;
+
 
 /**
- * An example runner for Multiclass to Binary Reduction with One Vs Rest.
- * The example uses Logistic Regression as the base classifier. All parameters that
- * can be specified on the base classifier can be passed in to the runner options.
+ * An example of Multiclass to Binary Reduction with One Vs Rest,
+ * using Logistic Regression as the base classifier.
  * Run with
  * <pre>
- * bin/run-example ml.JavaOneVsRestExample [options]
+ * bin/run-example ml.JavaOneVsRestExample
  * </pre>
  */
 public class JavaOneVsRestExample {
-
-  private static class Params {
-    String input;
-    String testInput = null;
-    Integer maxIter = 100;
-    double tol = 1E-6;
-    boolean fitIntercept = true;
-    Double regParam = null;
-    Double elasticNetParam = null;
-    double fracTest = 0.2;
-  }
-
   public static void main(String[] args) {
-    // parse the arguments
-    Params params = parse(args);
     SparkSession spark = SparkSession
       .builder()
       .appName("JavaOneVsRestExample")
       .getOrCreate();
 
     // $example on$
-    // configure the base classifier
-    LogisticRegression classifier = new LogisticRegression()
-      .setMaxIter(params.maxIter)
-      .setTol(params.tol)
-      .setFitIntercept(params.fitIntercept);
+    // load data file.
+    Dataset<Row> inputData = spark.read().format("libsvm")
+      .load("data/mllib/sample_multiclass_classification_data.txt");
 
-    if (params.regParam != null) {
-      classifier.setRegParam(params.regParam);
-    }
-    if (params.elasticNetParam != null) {
-      classifier.setElasticNetParam(params.elasticNetParam);
-    }
+    // generate the train/test split.
+    Dataset<Row>[] tmp = inputData.randomSplit(new double[]{0.8, 0.2});
+    Dataset<Row> train = tmp[0];
+    Dataset<Row> test = tmp[1];
 
-    // instantiate the One Vs Rest Classifier
-    OneVsRest ovr = new OneVsRest().setClassifier(classifier);
-
-    String input = params.input;
-    Dataset<Row> inputData = spark.read().format("libsvm").load(input);
-    Dataset<Row> train;
-    Dataset<Row> test;
+    // configure the base classifier.
+    LogisticRegression classifier = new LogisticRegression()
+      .setMaxIter(10)
+      .setTol(1E-6)
+      .setFitIntercept(true);
 
-    // compute the train/ test split: if testInput is not provided use part of input
-    String testInput = params.testInput;
-    if (testInput != null) {
-      train = inputData;
-      // compute the number of features in the training set.
-      int numFeatures = inputData.first().<Vector>getAs(1).size();
-      test = spark.read().format("libsvm").option("numFeatures",
-        String.valueOf(numFeatures)).load(testInput);
-    } else {
-      double f = params.fracTest;
-      Dataset<Row>[] tmp = inputData.randomSplit(new double[]{1 - f, f}, 12345);
-      train = tmp[0];
-      test = tmp[1];
-    }
+    // instantiate the One Vs Rest Classifier.
+    OneVsRest ovr = new OneVsRest().setClassifier(classifier);
 
-    // train the multiclass model
-    OneVsRestModel ovrModel = ovr.fit(train.cache());
+    // train the multiclass model.
+    OneVsRestModel ovrModel = ovr.fit(train);
 
-    // score the model on test data
-    Dataset<Row> predictions = ovrModel.transform(test.cache())
+    // score the model on test data.
+    Dataset<Row> predictions = ovrModel.transform(test)
       .select("prediction", "label");
 
-    // obtain metrics
-    MulticlassMetrics metrics = new MulticlassMetrics(predictions);
-    StructField predictionColSchema = predictions.schema().apply("prediction");
-    Integer numClasses = (Integer) MetadataUtils.getNumClasses(predictionColSchema).get();
-
-    // compute the false positive rate per label
-    StringBuilder results = new StringBuilder();
-    results.append("label\tfpr\n");
-    for (int label = 0; label < numClasses; label++) {
-      results.append(label);
-      results.append("\t");
-      results.append(metrics.falsePositiveRate((double) label));
-      results.append("\n");
-    }
+    // obtain evaluator.
+    MulticlassClassificationEvaluator evaluator = new MulticlassClassificationEvaluator()
+            .setMetricName("precision");
 
-    Matrix confusionMatrix = metrics.confusionMatrix();
-    // output the Confusion Matrix
-    System.out.println("Confusion Matrix");
-    System.out.println(confusionMatrix);
-    System.out.println();
-    System.out.println(results);
+    // compute the classification error on test data.
+    double precision = evaluator.evaluate(predictions);
+    System.out.println("Test Error : " + (1 - precision));
     // $example off$
 
     spark.stop();
   }
 
-  private static Params parse(String[] args) {
-    Options options = generateCommandlineOptions();
-    CommandLineParser parser = new PosixParser();
-    Params params = new Params();
-
-    try {
-      CommandLine cmd = parser.parse(options, args);
-      String value;
-      if (cmd.hasOption("input")) {
-        params.input = cmd.getOptionValue("input");
-      }
-      if (cmd.hasOption("maxIter")) {
-        value = cmd.getOptionValue("maxIter");
-        params.maxIter = Integer.parseInt(value);
-      }
-      if (cmd.hasOption("tol")) {
-        value = cmd.getOptionValue("tol");
-        params.tol = Double.parseDouble(value);
-      }
-      if (cmd.hasOption("fitIntercept")) {
-        value = cmd.getOptionValue("fitIntercept");
-        params.fitIntercept = Boolean.parseBoolean(value);
-      }
-      if (cmd.hasOption("regParam")) {
-        value = cmd.getOptionValue("regParam");
-        params.regParam = Double.parseDouble(value);
-      }
-      if (cmd.hasOption("elasticNetParam")) {
-        value = cmd.getOptionValue("elasticNetParam");
-        params.elasticNetParam = Double.parseDouble(value);
-      }
-      if (cmd.hasOption("testInput")) {
-        value = cmd.getOptionValue("testInput");
-        params.testInput = value;
-      }
-      if (cmd.hasOption("fracTest")) {
-        value = cmd.getOptionValue("fracTest");
-        params.fracTest = Double.parseDouble(value);
-      }
-
-    } catch (ParseException e) {
-      printHelpAndQuit(options);
-    }
-    return params;
-  }
-
-  @SuppressWarnings("static")
-  private static Options generateCommandlineOptions() {
-    Option input = OptionBuilder.withArgName("input")
-      .hasArg()
-      .isRequired()
-      .withDescription("input path to labeled examples. This path must be specified")
-      .create("input");
-    Option testInput = OptionBuilder.withArgName("testInput")
-      .hasArg()
-      .withDescription("input path to test examples")
-      .create("testInput");
-    Option fracTest = OptionBuilder.withArgName("testInput")
-      .hasArg()
-      .withDescription("fraction of data to hold out for testing." +
-        " If given option testInput, this option is ignored. default: 0.2")
-      .create("fracTest");
-    Option maxIter = OptionBuilder.withArgName("maxIter")
-      .hasArg()
-      .withDescription("maximum number of iterations for Logistic Regression. default:100")
-      .create("maxIter");
-    Option tol = OptionBuilder.withArgName("tol")
-      .hasArg()
-      .withDescription("the convergence tolerance of iterations " +
-        "for Logistic Regression. default: 1E-6")
-      .create("tol");
-    Option fitIntercept = OptionBuilder.withArgName("fitIntercept")
-      .hasArg()
-      .withDescription("fit intercept for logistic regression. default true")
-      .create("fitIntercept");
-    Option regParam = OptionBuilder.withArgName( "regParam" )
-      .hasArg()
-      .withDescription("the regularization parameter for Logistic Regression.")
-      .create("regParam");
-    Option elasticNetParam = OptionBuilder.withArgName("elasticNetParam" )
-      .hasArg()
-      .withDescription("the ElasticNet mixing parameter for Logistic Regression.")
-      .create("elasticNetParam");
-
-    Options options = new Options()
-      .addOption(input)
-      .addOption(testInput)
-      .addOption(fracTest)
-      .addOption(maxIter)
-      .addOption(tol)
-      .addOption(fitIntercept)
-      .addOption(regParam)
-      .addOption(elasticNetParam);
-
-    return options;
-  }
-
-  private static void printHelpAndQuit(Options options) {
-    HelpFormatter formatter = new HelpFormatter();
-    formatter.printHelp("JavaOneVsRestExample", options);
-    System.exit(-1);
-  }
 }