code: def df_to_simple_rdd(df, categorical=False, nb_classes=None, features_col='features', label_col='label'):
      
      sql_context = df.sql_ctx
      sql_context.registerDataFrameAsTable(df, "temp_table")
      selected_df = sql_context.sql(
          "SELECT {0} AS features, {1} as label from temp_table".format(features_col, label_col))
      if isinstance(selected_df.first().features, MLLibVector):
          lp_rdd = selected_df.rdd.map(
              lambda row: LabeledPoint(row.label, row.features))
      else:
          lp_rdd = selected_df.rdd.map(lambda row: LabeledPoint(
              row.label, MLLibVectors.fromML(row.features)))
      rdd = lp_to_simple_rdd(lp_rdd, categorical, nb_classes)
      return rdd
docs: Convert DataFrame into RDD of pairs