fix(butterfilter): robustly deals with NaN now

butterfilter.py

@@ -24,5 +24,14 @@ def butterfilter(timeseries, params=None):
     timeseries_norm = timeseries - np.nanmean(timeseries, axis=1).reshape(
         timeseries.shape[0], 1
     )
-    filtered_timeseries = signal.sosfiltfilt(sos, timeseries_norm, axis=1)
+    if np.any(np.isnan(timeseries_norm)):
+        # filter one at a time because of NaNs at different times
+        filtered_timeseries = np.nan * np.ones(timeseries_norm.shape)
+        for i in range(timeseries_norm.shape[0]):
+            data = timeseries_norm[i, :]
+            filtered = signal.sosfiltfilt(sos, data[~np.isnan(data)])
+            filtered_timeseries[i, ~np.isnan(data)] = filtered
+    else:
+        # filter all at once
+        filtered_timeseries = signal.sosfiltfilt(sos, timeseries_norm, axis=1)
     return filtered_timeseries