Fix decluster for detections at the same time (eqcorrscan#269)

CHANGES.md

@@ -3,6 +3,8 @@
 * Fix bug where `set_xcorr` as context manager did not correctly reset
   stream_xcorr methods.
 * Correct test-script (`test_eqcorrscan.py`) to find paths properly.
+* BUG-FIX in `Party.decluster` when detections made at exactly the same time
+  the first, rather than the highest of these was taken.
 
 ## 0.3.2
 * Implement reading Party objects from multiple files, including wildcard

eqcorrscan/core/match_filter.py

@@ -610,12 +610,16 @@ def decluster(self, trig_int, timing='detect', metric='avg_cor'):
         detect_times = np.array([
             _total_microsec(d[0].datetime, min_det.datetime)
             for d in detect_info])
+        # Trig_int must be converted from seconds to micro-seconds
         peaks_out = decluster(
             peaks=detect_vals, index=detect_times, trig_int=trig_int * 10 ** 6)
-        # Trig_int must be converted from seconds to micro-seconds
-        declustered_detections = [
-            all_detections[np.where(detect_times == ind[1])[0][0]]
-            for ind in peaks_out]
+        # Need to match both the time and the detection value
+        declustered_detections = []
+        for ind in peaks_out:
+            matching_time_indeces = np.where(detect_times == ind[-1])[0]
+            matches = matching_time_indeces[
+                np.where(detect_vals[matching_time_indeces] == ind[0])[0][0]]
+            declustered_detections.append(all_detections[matches])
         # Convert this list into families
         template_names = list(set([d.template_name
                                    for d in declustered_detections]))

eqcorrscan/tests/match_filter_test.py

@@ -1019,6 +1019,31 @@ def test_party_decluster(self):
                     self.party.copy().decluster(
                         trig_int=trig_int, timing='origin', metric=metric)
 
+    def test_party_decluster_same_times(self):
+        """
+        Test that the correct detection is associated with the peak.
+        Tests for the case where two detections from different templates are
+        made at the same time - the peak-finding finds the best, but decluster
+        did not always correctly associate the correct detection with that
+        peak.
+        """
+        # Test insertion before
+        test_party = self.party.copy()
+        det = test_party[0][0].copy()
+        det.detect_time = test_party[1][0].detect_time
+        det.detect_val = 4
+        test_party[0].detections.append(det)
+        test_party.decluster(1)
+        assert det not in [d for f in test_party for d in f]
+        # Tes insertion after
+        test_party = self.party.copy()
+        det = test_party[1][0].copy()
+        det.detect_time = test_party[0][0].detect_time
+        det.detect_val = 4
+        test_party[1].detections.append(det)
+        test_party.decluster(1)
+        assert det not in [d for f in test_party for d in f]
+
     def test_party_rethreshold(self):
         """Make sure that rethresholding removes the events we want it to."""
         party = self.party.copy()