title: Creation of Dense Vectors using Dataset API
body: <p>My dataset has multiple columns and I want to create feature vector with selective columns. I tried using VectorAssembler of  org.apache.spark.ml.feature.VectorAssembler package but since my dataset has multiple null values, the transform method of VectorAssembler is failing. 
  Is there any substitute for VectorAssembler? 
  Any other method to create Dense Vectors that can be passed to machine learning classification models?</p>