title: Removing Blank Strings from a Spark Dataframe
body: <p>Attempting to remove rows in which a Spark dataframe column contains blank strings. Originally did <code>val df2 = df1.na.drop()</code> but it turns out many of these values are being encoded as <code>""</code>.</p>
  
  <p>I'm stuck using Spark 1.3.1 and also cannot rely on DSL. (Importing spark.implicit_ isn't working.)</p>