fixing some more copywarnings

rowers/views/analysisviews.py

@@ -433,12 +433,12 @@ def trendflexdata(workouts, options,userid=0):
     if groupby != 'date':
         try:
             df['groupval'] = groups.mean()[groupby]
-            df['groupval'].loc[mask] = np.nan
+            df.loc[mask,'groupval'] = np.nan
 
             groupcols = df['groupval']
         except (ValueError, AttributeError): # pragma: no cover
             df['groupval'] =  groups.mean()[groupby].fillna(value=0)
-            df['groupval'].loc[mask] = np.nan
+            df.loc[mask,'groupval'] = np.nan
             groupcols = df['groupval']
         except KeyError: # pragma: no cover
             messages.error(request,'Data selection error')