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我一直在使用org.apache.spark.ml.Pipeline进行机器学习任务。了解实际概率而不仅仅是预测标签尤为重要,而且我很难得到它。这里我正在做随机森林的二元分类任务。班级标签是“是”和“否”。我想输出标签“是”的概率。概率存储在DenseVector中作为流水线输出,例如[0.69,0.31],但我不知道哪一个对应于“是”(0.69或0.31?)。我想应该有一些从labelIndexer检索它?如何从Spark ML随机森林中获得对应于该类的概率
这里是我的训练模型
val sc = new SparkContext(new SparkConf().setAppName(" ML").setMaster("local"))
val data = .... // load data from file
val df = sqlContext.createDataFrame(data).toDF("label", "features")
val labelIndexer = new StringIndexer()
.setInputCol("label")
.setOutputCol("indexedLabel")
.fit(df)
val featureIndexer = new VectorIndexer()
.setInputCol("features")
.setOutputCol("indexedFeatures")
.setMaxCategories(2)
.fit(df)
// Convert indexed labels back to original labels.
val labelConverter = new IndexToString()
.setInputCol("prediction")
.setOutputCol("predictedLabel")
.setLabels(labelIndexer.labels)
val Array(trainingData, testData) = df.randomSplit(Array(0.7, 0.3))
// Train a RandomForest model.
val rf = new RandomForestClassifier()
.setLabelCol("indexedLabel")
.setFeaturesCol("indexedFeatures")
.setNumTrees(10)
.setFeatureSubsetStrategy("auto")
.setImpurity("gini")
.setMaxDepth(4)
.setMaxBins(32)
// Create pipeline
val pipeline = new Pipeline()
.setStages(Array(labelIndexer, featureIndexer, rf,labelConverter))
// Train model
val model = pipeline.fit(trainingData)
// Save model
sc.parallelize(Seq(model), 1).saveAsObjectFile("/my/path/pipeline")
然后我将加载管道,并就新的数据预测的任务代码,这里是一段代码
// Ignoring loading data part
// Create DF
val testdf = sqlContext.createDataFrame(testData).toDF("features", "line")
// Load pipeline
val model = sc.objectFile[org.apache.spark.ml.PipelineModel]("/my/path/pipeline").first
// My Question comes here : How to extract the probability that corresponding to class label "1"
// This is my attempt, I would like to output probability for label "Yes" and predicted label . The probabilities are stored in a denseVector, but I don't know which one is corresponding to "Yes". Something like this:
val predictions = model.transform(testdf).select("probability").map(e=> e.asInstanceOf[DenseVector])
参考关于向RF的概率和标签: http://spark.apache.org/docs/latest/ml-classification-regression.html#random-forests
你说的意思是什么这个“我想输出概率标有‘1’,并预测标签。这些概率存储在DenseVector作为管道输出,但我不知道哪一个是对应的到“1”。“? – eliasah
嗨,我已经更新了说明。基本上我想输出对应于标签“是”的概率。 – Qing