[SPARK-11895][ML] rename and refactor DatasetExample under mllib/examples

We used the name `Dataset` to refer to `SchemaRDD` in 1.2 in ML pipelines and created this example file. Since `Dataset` has a new meaning in Spark 1.6, we should rename it to avoid confusion. This PR also removes support for dense format to simplify the example code.

cc: yinxusen

Author: Xiangrui Meng <meng@databricks.com>

Closes #9873 from mengxr/SPARK-11895.

examples/src/main/scala/org/apache/spark/examples/mllib/DatasetExample.scala → examples/src/main/scala/org/apache/spark/examples/ml/DataFrameExample.scala

@@ -16,7 +16,7 @@
  */
 
 // scalastyle:off println
-package org.apache.spark.examples.mllib
+package org.apache.spark.examples.ml
 
 import java.io.File
 
@@ -24,25 +24,22 @@ import com.google.common.io.Files
 import scopt.OptionParser
 
 import org.apache.spark.{SparkConf, SparkContext}
+import org.apache.spark.examples.mllib.AbstractParams
 import org.apache.spark.mllib.linalg.Vector
-import org.apache.spark.mllib.regression.LabeledPoint
 import org.apache.spark.mllib.stat.MultivariateOnlineSummarizer
-import org.apache.spark.mllib.util.MLUtils
-import org.apache.spark.rdd.RDD
-import org.apache.spark.sql.{Row, SQLContext, DataFrame}
+import org.apache.spark.sql.{DataFrame, Row, SQLContext}
 
 /**
- * An example of how to use [[org.apache.spark.sql.DataFrame]] as a Dataset for ML. Run with
+ * An example of how to use [[org.apache.spark.sql.DataFrame]] for ML. Run with
  * {{{
- * ./bin/run-example org.apache.spark.examples.mllib.DatasetExample [options]
+ * ./bin/run-example ml.DataFrameExample [options]
  * }}}
  * If you use it as a template to create your own app, please use `spark-submit` to submit your app.
  */
-object DatasetExample {
+object DataFrameExample {
 
-  case class Params(
-      input: String = "data/mllib/sample_libsvm_data.txt",
-      dataFormat: String = "libsvm") extends AbstractParams[Params]
+  case class Params(input: String = "data/mllib/sample_libsvm_data.txt")
+    extends AbstractParams[Params]
 
   def main(args: Array[String]) {
     val defaultParams = Params()
@@ -52,9 +49,6 @@ object DatasetExample {
       opt[String]("input")
         .text(s"input path to dataset")
         .action((x, c) => c.copy(input = x))
-      opt[String]("dataFormat")
-        .text("data format: libsvm (default), dense (deprecated in Spark v1.1)")
-        .action((x, c) => c.copy(input = x))
       checkConfig { params =>
         success
       }
@@ -69,55 +63,42 @@ object DatasetExample {
 
   def run(params: Params) {
 
-    val conf = new SparkConf().setAppName(s"DatasetExample with $params")
+    val conf = new SparkConf().setAppName(s"DataFrameExample with $params")
     val sc = new SparkContext(conf)
     val sqlContext = new SQLContext(sc)
-    import sqlContext.implicits._  // for implicit conversions
 
     // Load input data
-    val origData: RDD[LabeledPoint] = params.dataFormat match {
-      case "dense" => MLUtils.loadLabeledPoints(sc, params.input)
-      case "libsvm" => MLUtils.loadLibSVMFile(sc, params.input)
-    }
-    println(s"Loaded ${origData.count()} instances from file: ${params.input}")
-
-    // Convert input data to DataFrame explicitly.
-    val df: DataFrame = origData.toDF()
-    println(s"Inferred schema:\n${df.schema.prettyJson}")
-    println(s"Converted to DataFrame with ${df.count()} records")
-
-    // Select columns
-    val labelsDf: DataFrame = df.select("label")
-    val labels: RDD[Double] = labelsDf.map { case Row(v: Double) => v }
-    val numLabels = labels.count()
-    val meanLabel = labels.fold(0.0)(_ + _) / numLabels
-    println(s"Selected label column with average value $meanLabel")
-
-    val featuresDf: DataFrame = df.select("features")
-    val features: RDD[Vector] = featuresDf.map { case Row(v: Vector) => v }
+    println(s"Loading LIBSVM file with UDT from ${params.input}.")
+    val df: DataFrame = sqlContext.read.format("libsvm").load(params.input).cache()
+    println("Schema from LIBSVM:")
+    df.printSchema()
+    println(s"Loaded training data as a DataFrame with ${df.count()} records.")
+
+    // Show statistical summary of labels.
+    val labelSummary = df.describe("label")
+    labelSummary.show()
+
+    // Convert features column to an RDD of vectors.
+    val features = df.select("features").map { case Row(v: Vector) => v }
     val featureSummary = features.aggregate(new MultivariateOnlineSummarizer())(
       (summary, feat) => summary.add(feat),
       (sum1, sum2) => sum1.merge(sum2))
     println(s"Selected features column with average values:\n ${featureSummary.mean.toString}")
 
+    // Save the records in a parquet file.
     val tmpDir = Files.createTempDir()
     tmpDir.deleteOnExit()
     val outputDir = new File(tmpDir, "dataset").toString
     println(s"Saving to $outputDir as Parquet file.")
     df.write.parquet(outputDir)
 
+    // Load the records back.
     println(s"Loading Parquet file with UDT from $outputDir.")
-    val newDataset = sqlContext.read.parquet(outputDir)
-
-    println(s"Schema from Parquet: ${newDataset.schema.prettyJson}")
-    val newFeatures = newDataset.select("features").map { case Row(v: Vector) => v }
-    val newFeaturesSummary = newFeatures.aggregate(new MultivariateOnlineSummarizer())(
-      (summary, feat) => summary.add(feat),
-      (sum1, sum2) => sum1.merge(sum2))
-    println(s"Selected features column with average values:\n ${newFeaturesSummary.mean.toString}")
+    val newDF = sqlContext.read.parquet(outputDir)
+    println(s"Schema from Parquet:")
+    newDF.printSchema()
 
     sc.stop()
   }
-
 }
 // scalastyle:on println