clustering

공식 documentation : 

- https://spark.apache.org/docs/latest/ml-clustering.html

- https://spark.apache.org/docs/latest/api/python/reference/api/pyspark.ml.clustering.KMeans.html#pyspark.ml.clustering.KMeans.weightCol

- evaluate : https://spark.apache.org/docs/latest/api/python/reference/api/pyspark.ml.evaluation.ClusteringEvaluator.html