Update test_validation.py and validation.py

Author: alexlib

openpiv/test/test_validation.py

@@ -170,4 +170,36 @@ def test_global_val(N=2,U=(-10,10)):
     assert np.isnan(v1.data[0,0])
     print(mask1)
     assert mask1[N,N]
+    assert mask1[0,0]
+
+
+def test_global_std(N=2,std_threshold=3):
+    u = np.random.rand(2*N+1, 2*N+1)
+    u[N, N] = np.nanstd(u)*threshold + 1.
+    u[0,0] =  np.nanstd(u)*threshold + 1.
+
+    v = np.ma.masked_array(u.copy(), np.ma.nomask)
+    v[N+1,N+1] = np.ma.masked
+    
+    
+    print('data')
+    print(u)    
+    
+    
+    print('masked')
+    print(v.data)
+    print(v.mask)
+
+    u1, _, mask = validation.global_std(u, u, std_threshold=3)
+    assert np.isnan(u1[N,N])
+    assert np.isnan(u1[0,0])
+    assert mask[N,N]
+    assert mask[0,0]
+
+    v1, _, mask1 = validation.global_std(v, v, std_threshold=3)
+    assert isinstance(v1,np.ma.MaskedArray)
+    assert np.isnan(v1.data[N,N])
+    assert np.isnan(v1.data[0,0])
+    print(mask1)
+    assert mask1[N,N]
     assert mask1[0,0]

openpiv/validation.py

@@ -116,11 +116,11 @@ def global_std(u, v, std_threshold=3):
     # participating in the magnitude comparison
 
     if isinstance(u, np.ma.MaskedArray):
-        vel_magnitude = u.data ** 2 + v.data ** 2
+        vel_magnitude = u.filled(np.nan) ** 2 + v.filled(np.nan) ** 2
     else:
         vel_magnitude = u ** 2 + v ** 2
 
-    ind = vel_magnitude > std_threshold * np.std(vel_magnitude)
+    ind = vel_magnitude > std_threshold * np.nanstd(vel_magnitude)
 
     u[ind] = np.nan
     v[ind] = np.nan