Scala在if-else语句中赋值
对scala来说是个新手 我有一个if-else语句,它基于一个条件,为一个变量赋值Scala在if-else语句中赋值,scala,apache-spark,apache-spark-sql,apache-spark-mllib,Scala,Apache Spark,Apache Spark Sql,Apache Spark Mllib,对scala来说是个新手 我有一个if-else语句,它基于一个条件,为一个变量赋值 import org.apache.spark.ml.{Pipeline, PipelineModel, PipelineStage} modelType = "rf" def train(trainingData: DataFrame): PipelineModel = { val xgb = new XGBoostClassifier() .setLabelCol(
import org.apache.spark.ml.{Pipeline, PipelineModel, PipelineStage}
modelType = "rf"
def train(trainingData: DataFrame): PipelineModel = {
val xgb = new XGBoostClassifier()
.setLabelCol("label")
.setFeaturesCol("features")
.setObjective("binary:logistic")
.setEvalMetric("auc")
val rf = new RandomForestClassifier()
.setLabelCol("label")
.setFeaturesCol("features")
.setImpurity("gini")
if (modelType == "rf") {
val pipeline = new Pipeline()
.setStages(Array[PipelineStage](rf))
} else if (modelType == "xgb") {
val pipeline = new Pipeline()
.setStages(Array[PipelineStage](rf))
}
pipeline.fit(trainingData)
}
但我看到了这个错误:找不到管道。这是否意味着未分配管道变量?如何重写它?您将if设置为变量
val xgb = new XGBoostClassifier()
.setLabelCol("label")
.setFeaturesCol("features")
.setObjective("binary:logistic")
.setEvalMetric("auc")
val rf = new RandomForestClassifier()
.setLabelCol("label")
.setFeaturesCol("features")
.setImpurity("gini")
val pipeline = if (modelType == "rf") {
new Pipeline()
.setStages(Array[PipelineStage](rf))
} else if (modelType == "xgb") {
new Pipeline()
.setStages(Array[PipelineStage](rf))
}
}
pipeline.fit(trainingData)
}
一般来说,在包含if的then或else子句的块中定义的val只有在该块结束时才可见。@LeviRamsey感谢您的解释。我知道我的回答缺乏解释。我和OP有同样的问题,花了比我想承认的更多的时间寻找答案。我从来没有尝试过研究更多的语法,所以谢谢你!为了进一步阐明此操作的原因,当解析任何闭包时,它将解析为最后一行的值。在本例中,最后一行是新管道。