How to return a value to a val using if statement?-CodePudding

I am trying to convert a var assignment to a val assignment. Currently my code is

  // Numerical vectorizing for normalization
  var normNumericalColNameArray: Array[String] = Array()
  if (!continousPredictors.sameElements(Array(""))) {
    if (paramStandardize) {
      println("Apply standardization")
      stages  = new VectorAssembler().setInputCols(continousPredictors).setOutputCol(NumericalFeaturesCol)
      stages  = new StandardScaler()
        .setWithMean(true)
        .setWithStd(true)
        .setInputCol(NumericalFeaturesCol)
        .setOutputCol(StandardizedNumericalFeaturesCol)
      normNumericalColNameArray = Array(StandardizedNumericalFeaturesCol)
    } else {
      println("Not apply standardization")
      stages  = new VectorAssembler().setInputCols(continousPredictors).setOutputCol(NumericalFeaturesCol)
      normNumericalColNameArray = Array(NumericalFeaturesCol)
    }
  }

  stages  = new VectorAssembler().setInputCols(normNumericalColNameArray    oneHotCatColNamesArray).setOutputCol(FeaturesCol)

and I want to do something like this

  
  val normNumericalColNameArray =
    if (continousPredictors.nonEmpty && paramStandardize) {
    println("Apply standardization")
    stages  = new VectorAssembler().setInputCols(continousPredictors).setOutputCol(NumericalFeaturesCol)
    stages  = new StandardScaler()
      .setWithMean(true)
      .setWithStd(true)
      .setInputCol(NumericalFeaturesCol)
      .setOutputCol(StandardizedNumericalFeaturesCol)
    Array(StandardizedNumericalFeaturesCol)
    } else if (continousPredictors.nonEmpty){
    println("Not apply standardization")
    stages  = new VectorAssembler().setInputCols(continousPredictors).setOutputCol(NumericalFeaturesCol)
    Array(NumericalFeaturesCol)
    }


  stages  = new VectorAssembler().setInputCols(normNumericalColNameArray    oneHotCatColNamesArray).setOutputCol(FeaturesCol)

and I run into this error

value    is not a member of Any
stages  = new VectorAssembler().setInputCols(normNumericalColNameArray    oneHotCatColNamesArray).setOutputCol(FeaturesCol)

I am trying to return the Array from the if condition into my Val normNumericalColNameArray. Can somebody please help?

CodePudding user response：

The problem is that there is an if without an else block, so the result could be nothing (Unit). Just add an else clause:

} else if (continousPredictors.nonEmpty) {
  println("Not apply standardization")
  stages  = new VectorAssembler().setInputCols(continousPredictors).setOutputCol(NumericalFeaturesCol)

  Array(NumericalFeaturesCol)
} else {
  Array()
}

But Array is a Java type, so prefer to use Vector or List if possible.

CodePudding user response：

The problem is in the if statement. You have:

val normNumericalColNameArray = {
  if (condition1){
    return Array[String]()
  }
  else if (condition2){
    return Array[String]()
  }
}

Now, your variable has type Any because if condition1 is not true and condition2 is not true, then your if statement (function) doesn't return anything: you actually made a partial function. Try adding a final else statement, like:

val normNumericalColNameArray = {
  if (condition1){
    return Array[String]()
  }
  else if (condition2){
    return Array[String]()
  }
  else{
    return Array[String]()
  }
}

It will work then. Also, I would recommend to make your normNumericalColNameArray a lazy val, so to be evaluated only when it is required, since you are modifying stages in the if statement.