val resampledTrainDF = {

    val positiveLabel = "1"
    val trainDF_positives = trainDF.where(F.col(label) === positiveLabel)
    val trainDF_negatives = trainDF.where(F.col(label) =!= positiveLabel)

    val withReplacement = trainDF_positives.count >= trainDF_negatives.count

    if (withReplacement) {
        // downsampling positives
        val sampSize = math.round(  (1.0 * trainDF_negatives.count / trainDF_positives.count) * 1000) / 1000.0
        println("Downsampling Positives by " + (1 - sampSize)*100 + " %")
        trainDF_positives.sample(false, sampSize).union(trainDF_negatives)
    } else {
        //downsampling negatives
        val sampSize = math.round(  (1.0 * trainDF_positives.count / trainDF_negatives.count) * 1000) / 1000.0
        println("Downsampling Negatives by " + (1 - sampSize)*100 +  "%")
        trainDF_negatives.sample(false, sampSize).union(trainDF_positives)
    }

}