用scala语言交换两个变量 val numclass=5 val categorialfeaturesinfo=Map[Int，Int]（） val=“基尼” val maxDepth=0 val maxBins=32 val GRE精度=0 用于（最大深度精度）{ 准确度=准确度 } } println（“精度=”+greaccurity）

请帮忙 错误：重新分配到val 准确度=准确度

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val是不可变的变量，一旦设置，就无法更改它们。那是我设计的。另一方面，您可以更改它们

可能重复的

val numClasses = 5
val categoricalFeaturesInfo = Map[Int, Int]()
val impurity = "gini"
val maxDepth = 0
val maxBins = 32
val greaccuracy = 0
for( maxDepth <- 0 to 30){
val model = DecisionTree.trainClassifier(trainData, numClasses,  categoricalFeaturesInfo, impurity, maxDepth, maxBins)
val metrics = getMetrics(model, cvData)
val accuracy = metrics.precision
if (accuracy >  greaccuracy){
greaccuracy =  accuracy
}
}
println("Accuracy = "+greaccuracy)