Merge pull request #102 from g-kimbell/timestamp2

Bugfix timestamp interpolation

Author: d-cogswell

NewareNDA/NewareNDAx.py

@@ -154,9 +154,9 @@ def _data_interpolation(df):
     df['Time'] = df['Time'].where(nan_mask2, time)
 
     # Fill in missing Timestamps
-    time_inc = df['Time'].diff().groupby(nan_mask.cumsum()).cumsum()
+    time_inc = df['Time'].diff().groupby(nan_mask.shift().cumsum()).cumsum()
     timestamp = df['Timestamp'].ffill() + \
-        pd.to_timedelta(time_inc.shift().fillna(0), unit='s')
+        pd.to_timedelta(time_inc.fillna(0), unit='s')
     df['Timestamp'] = df['Timestamp'].where(nan_mask, timestamp)
 
     # Integrate to get capacity and fill missing values