smll bfx in multiva flagger

saqc/funcs/spikes_detection.py

@@ -176,6 +176,7 @@ def spikes_flagMultivarScores(data, field, flagger, fields, trafo=np.log, alpha=
 
 
     # data fransformation/extraction
+    val_frame = data[fields]
     val_frame = data.loc[data.index_of('shared')].to_df()
     val_frame.dropna(inplace=True)
     val_frame = val_frame.apply(trafo)