Fix ROC Component (#559)

* Fix ROC component.

* fix ROC component.

* Follow up on CR comments.

components/local/roc/src/roc.py

@@ -32,20 +32,29 @@
 def main(argv=None):
   parser = argparse.ArgumentParser(description='ML Trainer')
   parser.add_argument('--predictions', type=str, help='GCS path of prediction file pattern.')
-  parser.add_argument('--trueclass', type=str, help='The name of the class as true value.')
+  parser.add_argument('--trueclass', type=str, default='true',
+                      help='The name of the class as true value. If missing, assuming it is ' +
+                           'binary classification and default to "true".')
+  parser.add_argument('--true_score_column', type=str, default='true',
+                      help='The name of the column for positive prob. If missing, assuming it is ' +
+                           'binary classification and defaults to "true".')
   parser.add_argument('--target_lambda', type=str,
                       help='a lambda function as a string to determine positive or negative.' +
                            'For example, "lambda x: x[\'a\'] and x[\'b\']". If missing, ' +
-                           'trueclass must be set and input must have a "target" column.')
+                           'input must have a "target" column.')
   parser.add_argument('--output', type=str, help='GCS path of the output directory.')
   args = parser.parse_args()
 
-  if not args.target_lambda and not args.trueclass:
-    raise ValueError('Either target_lambda or trueclass must be set.')
-
   schema_file = os.path.join(os.path.dirname(args.predictions), 'schema.json')
   schema = json.loads(file_io.read_file_to_string(schema_file))
   names = [x['name'] for x in schema]
+
+  if not args.target_lambda and 'target' not in names:
+    raise ValueError('There is no "target" column, and target_lambda is not provided.')
+
+  if args.true_score_column not in names:
+    raise ValueError('Cannot find column name "%s"' % args.true_score_column)
+
   dfs = []
   files = file_io.get_matching_files(args.predictions)
   for file in files:
@@ -57,8 +66,8 @@ def main(argv=None):
     df['target'] = df.apply(eval(args.target_lambda), axis=1)
   else:
     df['target'] = df['target'].apply(lambda x: 1 if x == args.trueclass else 0)
-  fpr, tpr, thresholds = roc_curve(df['target'], df[args.trueclass])
-  roc_auc = roc_auc_score(df['target'], df[args.trueclass])
+  fpr, tpr, thresholds = roc_curve(df['target'], df[args.true_score_column])
+  roc_auc = roc_auc_score(df['target'], df[args.true_score_column])
   df_roc = pd.DataFrame({'fpr': fpr, 'tpr': tpr, 'thresholds': thresholds})
   roc_file = os.path.join(args.output, 'roc.csv')
   with file_io.FileIO(roc_file, 'w') as f: