Fix err computation for undefined variances

spacetelescope · Dec 12, 2024 · 7531f55 · 7531f55
1 parent d23e4a1
commit 7531f55
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Showing 2 changed files with 9 additions and 4 deletions.
diff --git a/jwst/resample/resample.py b/jwst/resample/resample.py
@@ -496,7 +496,12 @@ def resample_many_to_one(self, input_models):
                 valid_var.append(var)
             setattr(output_model, name, var)
 
-        err = np.sum(valid_var, axis=0).astype(np.float32)
+        if len(valid_var) > 0:
+            all_nan = np.all(np.isnan(valid_var), axis=0)
+            err = np.sqrt(np.nansum(valid_var, axis=0)).astype(np.float32)
+            err[all_nan] = np.nan
+        else:
+            err = np.full_like(output_model.data, np.nan)
         output_model.err = err
         del driz, err, valid_var, var
 

diff --git a/jwst/resample/tests/test_resample_step.py b/jwst/resample/tests/test_resample_step.py
@@ -809,8 +809,8 @@ def test_resample_variance(nircam_rate, n_images, weight_type):
 
     assert np.all((result1.err[mask] / err) <= 1.0)
     assert_allclose(
-        np.sum(result.err[mask]**2) * twht**2,
-        np.sum(result1.err[mask]**2) * twht1**2,
+        np.sum(result.err[mask]**2) * twht,
+        np.sum(result1.err[mask]**2) * twht1,
         rtol=1e-6,
         atol=0.0,
     )
@@ -849,7 +849,7 @@ def test_resample_undefined_variance(nircam_rate, shape):
         result = ResampleStep.call(c, blendheaders=False)
 
     # no valid variance - variance are all NaN
-    assert np.any(np.isfinite(result.err))
+    assert_allclose(result.err, np.nan)
     assert_allclose(result.var_rnoise, np.nan)
     assert_allclose(result.var_poisson, np.nan)
     assert_allclose(result.var_flat, np.nan)