[SPARK-16421][EXAMPLES][ML] Improve ML Example Outputs

## What changes were proposed in this pull request?
Improve example outputs to better reflect the functionality that is being presented.  This mostly consisted of modifying what was printed at the end of the example, such as calling show() with truncate=False, but sometimes required minor tweaks in the example data to get relevant output.  Explicitly set parameters when they are used as part of the example.  Fixed Java examples that failed to run because of using old-style MLlib Vectors or problem with schema.  Synced examples between different APIs.

## How was this patch tested?
Ran each example for Scala, Python, and Java and made sure output was legible on a terminal of width 100.

Author: Bryan Cutler <cutlerb@gmail.com>

Closes apache#14308 from BryanCutler/ml-examples-improve-output-SPARK-16260.

examples/src/main/java/org/apache/spark/examples/JavaPageRank.java

@@ -45,6 +45,11 @@
  *
  * This is an example implementation for learning how to use Spark. For more conventional use,
  * please refer to org.apache.spark.graphx.lib.PageRank
+ *
+ * Example Usage:
+ * <pre>
+ * bin/run-example JavaPageRank data/mllib/pagerank_data.txt 10
+ * </pre>
  */
 public final class JavaPageRank {
   private static final Pattern SPACES = Pattern.compile("\\s+");

examples/src/main/java/org/apache/spark/examples/ml/JavaAFTSurvivalRegressionExample.java

@@ -71,8 +71,9 @@ public static void main(String[] args) {
     AFTSurvivalRegressionModel model = aft.fit(training);
 
     // Print the coefficients, intercept and scale parameter for AFT survival regression
-    System.out.println("Coefficients: " + model.coefficients() + " Intercept: "
-      + model.intercept() + " Scale: " + model.scale());
+    System.out.println("Coefficients: " + model.coefficients());
+    System.out.println("Intercept: " + model.intercept());
+    System.out.println("Scale: " + model.scale());
     model.transform(training).show(false);
     // $example off$
 

examples/src/main/java/org/apache/spark/examples/ml/JavaBinarizerExample.java

@@ -51,17 +51,18 @@ public static void main(String[] args) {
       new StructField("feature", DataTypes.DoubleType, false, Metadata.empty())
     });
     Dataset<Row> continuousDataFrame = spark.createDataFrame(data, schema);
+
     Binarizer binarizer = new Binarizer()
       .setInputCol("feature")
       .setOutputCol("binarized_feature")
       .setThreshold(0.5);
+
     Dataset<Row> binarizedDataFrame = binarizer.transform(continuousDataFrame);
-    Dataset<Row> binarizedFeatures = binarizedDataFrame.select("binarized_feature");
-    for (Row r : binarizedFeatures.collectAsList()) {
-      Double binarized_value = r.getDouble(0);
-      System.out.println(binarized_value);
-    }
+
+    System.out.println("Binarizer output with Threshold = " + binarizer.getThreshold());
+    binarizedDataFrame.show();
     // $example off$
+
     spark.stop();
   }
 }

examples/src/main/java/org/apache/spark/examples/ml/JavaBucketizerExample.java

@@ -44,10 +44,12 @@ public static void main(String[] args) {
     double[] splits = {Double.NEGATIVE_INFINITY, -0.5, 0.0, 0.5, Double.POSITIVE_INFINITY};
 
     List<Row> data = Arrays.asList(
+      RowFactory.create(-999.9),
       RowFactory.create(-0.5),
       RowFactory.create(-0.3),
       RowFactory.create(0.0),
-      RowFactory.create(0.2)
+      RowFactory.create(0.2),
+      RowFactory.create(999.9)
     );
     StructType schema = new StructType(new StructField[]{
       new StructField("features", DataTypes.DoubleType, false, Metadata.empty())
@@ -61,8 +63,11 @@ public static void main(String[] args) {
 
     // Transform original data into its bucket index.
     Dataset<Row> bucketedData = bucketizer.transform(dataFrame);
+
+    System.out.println("Bucketizer output with " + (bucketizer.getSplits().length-1) + " buckets");
     bucketedData.show();
     // $example off$
+
     spark.stop();
   }
 }

examples/src/main/java/org/apache/spark/examples/ml/JavaChiSqSelectorExample.java

@@ -63,7 +63,11 @@ public static void main(String[] args) {
       .setOutputCol("selectedFeatures");
 
     Dataset<Row> result = selector.fit(df).transform(df);
+
+    System.out.println("ChiSqSelector output with top " + selector.getNumTopFeatures()
+        + " features selected");
     result.show();
+
     // $example off$
     spark.stop();
   }

examples/src/main/java/org/apache/spark/examples/ml/JavaCountVectorizerExample.java

@@ -61,7 +61,7 @@ public static void main(String[] args) {
       .setInputCol("text")
       .setOutputCol("feature");
 
-    cvModel.transform(df).show();
+    cvModel.transform(df).show(false);
     // $example off$
 
     spark.stop();

examples/src/main/java/org/apache/spark/examples/ml/JavaDCTExample.java

@@ -51,13 +51,17 @@ public static void main(String[] args) {
       new StructField("features", new VectorUDT(), false, Metadata.empty()),
     });
     Dataset<Row> df = spark.createDataFrame(data, schema);
+
     DCT dct = new DCT()
       .setInputCol("features")
       .setOutputCol("featuresDCT")
       .setInverse(false);
+
     Dataset<Row> dctDf = dct.transform(df);
-    dctDf.select("featuresDCT").show(3);
+
+    dctDf.select("featuresDCT").show(false);
     // $example off$
+
     spark.stop();
   }
 }

examples/src/main/java/org/apache/spark/examples/ml/JavaGaussianMixtureExample.java

@@ -54,8 +54,8 @@ public static void main(String[] args) {
 
     // Output the parameters of the mixture model
     for (int i = 0; i < model.getK(); i++) {
-      System.out.printf("weight=%f\nmu=%s\nsigma=\n%s\n",
-              model.weights()[i], model.gaussians()[i].mean(), model.gaussians()[i].cov());
+      System.out.printf("Gaussian %d:\nweight=%f\nmu=%s\nsigma=\n%s\n\n",
+              i, model.weights()[i], model.gaussians()[i].mean(), model.gaussians()[i].cov());
     }
     // $example off$
 

examples/src/main/java/org/apache/spark/examples/ml/JavaIndexToStringExample.java

@@ -24,6 +24,7 @@
 import java.util.Arrays;
 import java.util.List;
 
+import org.apache.spark.ml.attribute.Attribute;
 import org.apache.spark.ml.feature.IndexToString;
 import org.apache.spark.ml.feature.StringIndexer;
 import org.apache.spark.ml.feature.StringIndexerModel;
@@ -63,11 +64,23 @@ public static void main(String[] args) {
       .fit(df);
     Dataset<Row> indexed = indexer.transform(df);
 
+    System.out.println("Transformed string column '" + indexer.getInputCol() + "' " +
+        "to indexed column '" + indexer.getOutputCol() + "'");
+    indexed.show();
+
+    StructField inputColSchema = indexed.schema().apply(indexer.getOutputCol());
+    System.out.println("StringIndexer will store labels in output column metadata: " +
+        Attribute.fromStructField(inputColSchema).toString() + "\n");
+
     IndexToString converter = new IndexToString()
       .setInputCol("categoryIndex")
       .setOutputCol("originalCategory");
     Dataset<Row> converted = converter.transform(indexed);
-    converted.select("id", "originalCategory").show();
+
+    System.out.println("Transformed indexed column '" + converter.getInputCol() + "' back to " +
+        "original string column '" + converter.getOutputCol() + "' using labels in metadata");
+    converted.select("id", "categoryIndex", "originalCategory").show();
+
     // $example off$
     spark.stop();
   }

examples/src/main/java/org/apache/spark/examples/ml/JavaIsotonicRegressionExample.java

@@ -50,8 +50,8 @@ public static void main(String[] args) {
     IsotonicRegression ir = new IsotonicRegression();
     IsotonicRegressionModel model = ir.fit(dataset);
 
-    System.out.println("Boundaries in increasing order: " + model.boundaries());
-    System.out.println("Predictions associated with the boundaries: " + model.predictions());
+    System.out.println("Boundaries in increasing order: " + model.boundaries() + "\n");
+    System.out.println("Predictions associated with the boundaries: " + model.predictions() + "\n");
 
     // Makes predictions.
     model.transform(dataset).show();

examples/src/main/java/org/apache/spark/examples/ml/JavaMaxAbsScalerExample.java

@@ -18,10 +18,20 @@
 package org.apache.spark.examples.ml;
 
 // $example on$
+import java.util.Arrays;
+import java.util.List;
+
 import org.apache.spark.ml.feature.MaxAbsScaler;
 import org.apache.spark.ml.feature.MaxAbsScalerModel;
+import org.apache.spark.ml.linalg.Vectors;
+import org.apache.spark.ml.linalg.VectorUDT;
 import org.apache.spark.sql.Dataset;
 import org.apache.spark.sql.Row;
+import org.apache.spark.sql.RowFactory;
+import org.apache.spark.sql.types.DataTypes;
+import org.apache.spark.sql.types.Metadata;
+import org.apache.spark.sql.types.StructField;
+import org.apache.spark.sql.types.StructType;
 // $example off$
 import org.apache.spark.sql.SparkSession;
 
@@ -34,10 +44,17 @@ public static void main(String[] args) {
       .getOrCreate();
 
     // $example on$
-    Dataset<Row> dataFrame = spark
-      .read()
-      .format("libsvm")
-      .load("data/mllib/sample_libsvm_data.txt");
+    List<Row> data = Arrays.asList(
+        RowFactory.create(0, Vectors.dense(1.0, 0.1, -8.0)),
+        RowFactory.create(1, Vectors.dense(2.0, 1.0, -4.0)),
+        RowFactory.create(2, Vectors.dense(4.0, 10.0, 8.0))
+    );
+    StructType schema = new StructType(new StructField[]{
+        new StructField("id", DataTypes.IntegerType, false, Metadata.empty()),
+        new StructField("features", new VectorUDT(), false, Metadata.empty())
+    });
+    Dataset<Row> dataFrame = spark.createDataFrame(data, schema);
+
     MaxAbsScaler scaler = new MaxAbsScaler()
       .setInputCol("features")
       .setOutputCol("scaledFeatures");
@@ -47,8 +64,9 @@ public static void main(String[] args) {
 
     // rescale each feature to range [-1, 1].
     Dataset<Row> scaledData = scalerModel.transform(dataFrame);
-    scaledData.show();
+    scaledData.select("features", "scaledFeatures").show();
     // $example off$
+
     spark.stop();
   }
 

examples/src/main/java/org/apache/spark/examples/ml/JavaMinMaxScalerExample.java

@@ -20,10 +20,20 @@
 import org.apache.spark.sql.SparkSession;
 
 // $example on$
+import java.util.Arrays;
+import java.util.List;
+
 import org.apache.spark.ml.feature.MinMaxScaler;
 import org.apache.spark.ml.feature.MinMaxScalerModel;
+import org.apache.spark.ml.linalg.Vectors;
+import org.apache.spark.ml.linalg.VectorUDT;
 import org.apache.spark.sql.Dataset;
 import org.apache.spark.sql.Row;
+import org.apache.spark.sql.RowFactory;
+import org.apache.spark.sql.types.DataTypes;
+import org.apache.spark.sql.types.Metadata;
+import org.apache.spark.sql.types.StructField;
+import org.apache.spark.sql.types.StructType;
 // $example off$
 
 public class JavaMinMaxScalerExample {
@@ -34,10 +44,17 @@ public static void main(String[] args) {
       .getOrCreate();
 
     // $example on$
-    Dataset<Row> dataFrame = spark
-      .read()
-      .format("libsvm")
-      .load("data/mllib/sample_libsvm_data.txt");
+    List<Row> data = Arrays.asList(
+        RowFactory.create(0, Vectors.dense(1.0, 0.1, -1.0)),
+        RowFactory.create(1, Vectors.dense(2.0, 1.1, 1.0)),
+        RowFactory.create(2, Vectors.dense(3.0, 10.1, 3.0))
+    );
+    StructType schema = new StructType(new StructField[]{
+        new StructField("id", DataTypes.IntegerType, false, Metadata.empty()),
+        new StructField("features", new VectorUDT(), false, Metadata.empty())
+    });
+    Dataset<Row> dataFrame = spark.createDataFrame(data, schema);
+
     MinMaxScaler scaler = new MinMaxScaler()
       .setInputCol("features")
       .setOutputCol("scaledFeatures");
@@ -47,8 +64,11 @@ public static void main(String[] args) {
 
     // rescale each feature to range [min, max].
     Dataset<Row> scaledData = scalerModel.transform(dataFrame);
-    scaledData.show();
+    System.out.println("Features scaled to range: [" + scaler.getMin() + ", "
+        + scaler.getMax() + "]");
+    scaledData.select("features", "scaledFeatures").show();
     // $example off$
+
     spark.stop();
   }
 }

examples/src/main/java/org/apache/spark/examples/ml/JavaMultilayerPerceptronClassifierExample.java

@@ -41,28 +41,34 @@ public static void main(String[] args) {
     // Load training data
     String path = "data/mllib/sample_multiclass_classification_data.txt";
     Dataset<Row> dataFrame = spark.read().format("libsvm").load(path);
+
     // Split the data into train and test
     Dataset<Row>[] splits = dataFrame.randomSplit(new double[]{0.6, 0.4}, 1234L);
     Dataset<Row> train = splits[0];
     Dataset<Row> test = splits[1];
+
     // specify layers for the neural network:
     // input layer of size 4 (features), two intermediate of size 5 and 4
     // and output of size 3 (classes)
     int[] layers = new int[] {4, 5, 4, 3};
+
     // create the trainer and set its parameters
     MultilayerPerceptronClassifier trainer = new MultilayerPerceptronClassifier()
       .setLayers(layers)
       .setBlockSize(128)
       .setSeed(1234L)
       .setMaxIter(100);
+
     // train the model
     MultilayerPerceptronClassificationModel model = trainer.fit(train);
+
     // compute accuracy on the test set
     Dataset<Row> result = model.transform(test);
     Dataset<Row> predictionAndLabels = result.select("prediction", "label");
     MulticlassClassificationEvaluator evaluator = new MulticlassClassificationEvaluator()
       .setMetricName("accuracy");
-    System.out.println("Accuracy = " + evaluator.evaluate(predictionAndLabels));
+
+    System.out.println("Test set accuracy = " + evaluator.evaluate(predictionAndLabels));
     // $example off$
 
     spark.stop();

examples/src/main/java/org/apache/spark/examples/ml/JavaNGramExample.java

@@ -42,29 +42,25 @@ public static void main(String[] args) {
 
     // $example on$
     List<Row> data = Arrays.asList(
-      RowFactory.create(0.0, Arrays.asList("Hi", "I", "heard", "about", "Spark")),
-      RowFactory.create(1.0, Arrays.asList("I", "wish", "Java", "could", "use", "case", "classes")),
-      RowFactory.create(2.0, Arrays.asList("Logistic", "regression", "models", "are", "neat"))
+      RowFactory.create(0, Arrays.asList("Hi", "I", "heard", "about", "Spark")),
+      RowFactory.create(1, Arrays.asList("I", "wish", "Java", "could", "use", "case", "classes")),
+      RowFactory.create(2, Arrays.asList("Logistic", "regression", "models", "are", "neat"))
     );
 
     StructType schema = new StructType(new StructField[]{
-      new StructField("label", DataTypes.DoubleType, false, Metadata.empty()),
+      new StructField("id", DataTypes.IntegerType, false, Metadata.empty()),
       new StructField(
         "words", DataTypes.createArrayType(DataTypes.StringType), false, Metadata.empty())
     });
 
     Dataset<Row> wordDataFrame = spark.createDataFrame(data, schema);
 
-    NGram ngramTransformer = new NGram().setInputCol("words").setOutputCol("ngrams");
+    NGram ngramTransformer = new NGram().setN(2).setInputCol("words").setOutputCol("ngrams");
 
     Dataset<Row> ngramDataFrame = ngramTransformer.transform(wordDataFrame);
-
-    for (Row r : ngramDataFrame.select("ngrams", "label").takeAsList(3)) {
-      java.util.List<String> ngrams = r.getList(0);
-      for (String ngram : ngrams) System.out.print(ngram + " --- ");
-      System.out.println();
-    }
+    ngramDataFrame.select("ngrams").show(false);
     // $example off$
+
     spark.stop();
   }
 }

examples/src/main/java/org/apache/spark/examples/ml/JavaNaiveBayesExample.java

@@ -48,14 +48,21 @@ public static void main(String[] args) {
 
     // create the trainer and set its parameters
     NaiveBayes nb = new NaiveBayes();
+
     // train the model
     NaiveBayesModel model = nb.fit(train);
+
+    // Select example rows to display.
+    Dataset<Row> predictions = model.transform(test);
+    predictions.show();
+
     // compute accuracy on the test set
-    Dataset<Row> result = model.transform(test);
-    Dataset<Row> predictionAndLabels = result.select("prediction", "label");
     MulticlassClassificationEvaluator evaluator = new MulticlassClassificationEvaluator()
+      .setLabelCol("label")
+      .setPredictionCol("prediction")
       .setMetricName("accuracy");
-    System.out.println("Accuracy = " + evaluator.evaluate(predictionAndLabels));
+    double accuracy = evaluator.evaluate(predictions);
+    System.out.println("Test set accuracy = " + accuracy);
     // $example off$
 
     spark.stop();