決策樹進(jìn)行鳶尾花分類的案例

背景說明：

通過IDEA + Spark 3.4.1 + sbt 1.9.3 + Spark MLlib 構(gòu)建鳶尾花決策樹分類預(yù)測(cè)模型，這是一個(gè)分類模型案例，通過該案例，可以快速了解Spark MLlib分類預(yù)測(cè)模型的使用方法。

依賴

ThisBuild / version := "0.1.0-SNAPSHOT"  
  
ThisBuild / scalaVersion := "2.13.11"  
  
lazy val root = (project in file("."))  
  .settings(  
    name := "SparkLearning",  
    idePackagePrefix := Some("cn.lh.spark"),  
    libraryDependencies += "org.apache.spark" %% "spark-sql" % "3.4.1",  
    libraryDependencies += "org.apache.spark" %% "spark-core" % "3.4.1",  
    libraryDependencies += "org.apache.hadoop" % "hadoop-auth" % "3.3.6",     libraryDependencies += "org.apache.spark" %% "spark-streaming" % "3.4.1",  
    libraryDependencies += "org.apache.spark" %% "spark-streaming-kafka-0-10" % "3.4.1",  
    libraryDependencies += "org.apache.spark" %% "spark-mllib" % "3.4.1",  
    libraryDependencies += "mysql" % "mysql-connector-java" % "8.0.30"  
)

完整代碼

package cn.lh.spark  
  
import org.apache.spark.ml.{Pipeline, PipelineModel}  
import org.apache.spark.ml.classification.{DecisionTreeClassificationModel, DecisionTreeClassifier}  
import org.apache.spark.ml.evaluation.MulticlassClassificationEvaluator  
import org.apache.spark.ml.feature.{IndexToString, StringIndexer, StringIndexerModel, VectorIndexer, VectorIndexerModel}  
import org.apache.spark.ml.linalg.Vectors  
import org.apache.spark.rdd.RDD  
import org.apache.spark.sql.{DataFrame, SparkSession}  
  
  
/**  
 * 決策樹分類器,實(shí)現(xiàn)鳶尾花分類  
 */  
  
//case class Iris(features: org.apache.spark.ml.linalg.Vector, label: String)  // MLlibLogisticRegression 中存在該樣例類，這里不用寫,一個(gè)包里不存在這個(gè)樣例類時(shí)需要寫
  
object MLlibDecisionTreeClassifier {  
  
  def main(args: Array[String]): Unit = {  
  
    val spark: SparkSession = SparkSession.builder().master("local[2]")  
      .appName("Spark MLlib DecisionTreeClassifier").getOrCreate()  
  
    val irisRDD: RDD[Iris] = spark.sparkContext.textFile("F:\\niit\\2023\\2023_2\\Spark\\codes\\data\\iris.txt")  
      .map(_.split(",")).map(p =>  
      Iris(Vectors.dense(p(0).toDouble, p(1).toDouble, p(2).toDouble, p(3).toDouble), p(4).toString()))  
  
    import spark.implicits._  
    val data: DataFrame = irisRDD.toDF()  
    data.show()  
  
    data.createOrReplaceTempView("iris")  
    val df: DataFrame = spark.sql("select * from iris")  
  
    println("鳶尾花原始數(shù)據(jù)如下：")  
    df.map(t => t(1)+":"+t(0)).collect().foreach(println)  
  
    //    處理特征和標(biāo)簽，以及數(shù)據(jù)分組  
    val labelIndexer: StringIndexerModel = new StringIndexer().setInputCol("label").setOutputCol(  
      "indexedLabel").fit(df)  
  
    val featureIndexer: VectorIndexerModel = new VectorIndexer().setInputCol("features")  
      .setOutputCol("indexedFeatures").setMaxCategories(4).fit(df)  
    //這里我們?cè)O(shè)置一個(gè)labelConverter，目的是把預(yù)測(cè)的類別重新轉(zhuǎn)化成字符型的  
    val labelConverter: IndexToString = new IndexToString().setInputCol("prediction")  
      .setOutputCol("predictedLabel").setLabels(labelIndexer.labels)  
  
    //接下來，我們把數(shù)據(jù)集隨機(jī)分成訓(xùn)練集和測(cè)試集，其中訓(xùn)練集占70%。  
    val Array(trainingData, testData) = data.randomSplit(Array(0.7, 0.3))  
  
    val dtClassifier: DecisionTreeClassifier = new DecisionTreeClassifier()  
      .setLabelCol("indexedLabel").setFeaturesCol("indexedFeatures")  
  
    //在pipeline中進(jìn)行設(shè)置  
    val pipelinedClassifier: Pipeline = new Pipeline()  
      .setStages(Array(labelIndexer, featureIndexer, dtClassifier, labelConverter))  
    //訓(xùn)練決策樹模型  
    val modelClassifier: PipelineModel = pipelinedClassifier.fit(trainingData)  
    //進(jìn)行預(yù)測(cè)  
    val predictionsClassifier: DataFrame = modelClassifier.transform(testData)  
    predictionsClassifier.select("predictedLabel", "label", "features").show(5)  
  
    //    評(píng)估決策樹分類模型  
    val evaluatorClassifier: MulticlassClassificationEvaluator = new MulticlassClassificationEvaluator()  
      .setLabelCol("indexedLabel")  
      .setPredictionCol("prediction").setMetricName("accuracy")  
    val accuracy: Double = evaluatorClassifier.evaluate(predictionsClassifier)  
    println("Test Error = " + (1.0 - accuracy))  
  
    val treeModelClassifier: DecisionTreeClassificationModel = modelClassifier.stages(2)  
      .asInstanceOf[DecisionTreeClassificationModel]  
  
    println("Learned classification tree model:\n" + treeModelClassifier.toDebugString)  
  
  
    spark.stop()  
  }  
  
}

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