title: Dropping a nested column from Spark DataFrame
body: <p>I have a <code>DataFrame</code> with the schema</p>
  
  <pre><code>root
   |-- label: string (nullable = true)
   |-- features: struct (nullable = true)
   |    |-- feat1: string (nullable = true)
   |    |-- feat2: string (nullable = true)
   |    |-- feat3: string (nullable = true)
  </code></pre>
  
  <p>While, I am able to filter the data frame using </p>
  
  <pre><code>  val data = rawData
       .filter( !(rawData("features.feat1") &lt;=&gt; "100") )
  </code></pre>
  
  <p>I am unable to drop the columns using </p>
  
  <pre><code>  val data = rawData
         .drop("features.feat1")
  </code></pre>
  
  <p>Is it something that I am doing wrong here? I also tried (unsuccessfully) doing <code>drop(rawData("features.feat1"))</code>, though it does not make much sense to do so. </p>
  
  <p>Thanks in advance,</p>
  
  <p>Nikhil</p>