title: How to get the numeric columns from DataFrame of Pyspark and calculating the zscore
body: <pre><code>sparkSession = SparkSession.builder.appName("example").getOrCreate()
  df = sparkSession.read.json('hdfs://localhost/abc/zscore/')
  </code></pre>
  
  <p>I am able to read the data from hdfs and I want to calculate the zscore for only numeric columns</p>