/// <summary>
/// Returns a new DataFrame with a column dropped.
/// Reference to https://github.com/apache/spark/blob/branch-1.4/python/pyspark/sql/dataframe.py, drop(self, col)
/// </summary>
/// <param name="columnName"> a string name of the column to drop</param>
/// <returns>A new new DataFrame that drops the specified column.</returns>
public DataFrame Drop(string columnName)
{
return
(new DataFrame(dataFrameProxy.Drop(columnName), sparkContext));
}