Fix grouper issue.

cdf_compare.py

@@ -37,7 +37,7 @@ def csv_to_dataframe(csv_list, folder, dummy):
         n.value += 1
 
     tmp_df = tmp_df.filter(
-        ["srtt", "datetime", "srtt", "payload_size", "congestion_control", "direction"])
+        ["srtt", "datetime", "payload_size", "congestion_control", "direction"])
     frame_list.append(tmp_df)
     del tmp_df