Merge pull request #105 from lsst/tickets/DM-18751

Use sample standard deviation for AMx.
lsst-dm · Aug 21, 2019 · 3c94890 · 3c94890
2 parents 5ca24d7 + 3d3e284
commit 3c94890
Showing 1 changed file with 3 additions and 2 deletions.
diff --git a/python/lsst/validate/drp/calcsrd/amx.py b/python/lsst/validate/drp/calcsrd/amx.py
@@ -208,9 +208,10 @@ def magInRange(cat):
                 continue
 
             finiteEntries, = np.where(np.isfinite(distances))
-            # Need at least 2 distances to get a nonzero stdev
+            # Need at least 2 distances to get a finite sample stdev
             if len(finiteEntries) > 1:
-                rmsDist = np.std(np.array(distances)[finiteEntries])
+                # ddof=1 to get sample standard deviation (e.g., 1/(n-1))
+                rmsDist = np.std(np.array(distances)[finiteEntries], ddof=1)
                 rmsDistances.append(rmsDist)
 
     # return quantity