title: Select columns from a dataframe into another dataframe based on column datatype in Apache Spark Scala
body: <p>I have a spark dataframe</p>
  
  <pre><code>inputDF: org.apache.spark.sql.DataFrame = [_id: string, Frequency:              double, Monterary: double, Recency: double, CustID: string]
          root
       |-- _id: string (nullable = false)
       |-- Frequency: double (nullable = false)
       |-- Monterary: double (nullable = false)
       |-- Recency: double (nullable = false)
       |-- CustID: string (nullable = false)
  </code></pre>
  
  <p>I want to create a new dataframe by dropping string columns from this. Specific condition is not to iterate over the column names .
  Anyone has any idea ?</p>