SparkML弯头图的问题

Question

我正在尝试使用SparkML Kmeans构建肘形图

我尝试设置种子，但是当我绘制曲线时，我发现SumOfSquaredDistance没有正确减小。

这是我当前的曲线current_elbow

有人有什么解释吗？

def getKmeansModel(k: Int, df_with_features: DataFrame,features_colname: String) : KMeansModel = {
  // Trains a k-means model.
  println("Trains a k-means model with n of clusters: "+k)
  val kmeans = new KMeans().setK(k).setSeed(123456789L).setFeaturesCol(features_colname)
  val model = kmeans.fit(df_with_features)
  model
}

def getKmeanWithinSetSumSquaredErrors(model: KMeansModel): (Int,Double) = { 
   val training_summary = model.summary
  (training_summary.k,training_summary.trainingCost) 
}

def getElbowDf(min_k: Int, max_k: Int, df_with_features: DataFrame,features_colname: String) : List[(Int, Double)] = 
{
  val range_list: List[Int] = min_k until max_k+1 toList
  var result = scala.collection.mutable.Map[Int, Double]()
  @tailrec
  def iter(range_list:List[Int], result:scala.collection.mutable.Map[Int,Double]):List[(Int, Double)] =
    if(range_list.isEmpty) result.toList
    else iter(range_list.tail,result + getKmeanWithinSetSumSquaredErrors(getKmeansModel(range_list.head,df_with_features,features_colname)))
  iter(range_list, result)
}