Don't set _finite if no data (#342)

docs/manual/references.rst

@@ -19,8 +19,12 @@ References
 .. [JoOM06] Jönsthövel, T. B., C. W. Oosterlee, and W. A. Mulder, 2006,
    Improving multigrid for 3-D electro-magnetic diffusion on stretched grids:
    European Conference on Computational Fluid Dynamics; UUID:
-   `df65da5c-e43f-47ab-b80d-2f8ee7f35464
-   <http://resolver.tudelft.nl/uuid:df65da5c-e43f-47ab-b80d-2f8ee7f35464>`_.
+   `632b503b-149a-47c1-a6b2-2f98f8703b48
+   <https://resolver.tudelft.nl/uuid:632b503b-149a-47c1-a6b2-2f98f8703b48>`_.
+
+   ..
+       df65da5c-e43f-47ab-b80d-2f8ee7f35464  # Old uuid
+
 .. [Hack85] Hackbusch, W., 1985, Multi-grid methods and applications: Springer,
    Berlin, Heidelberg, Volume 4 of Springer Series in Computational
    Mathematics; DOI: `10.1007/978- 3-662-02427-0 <https://doi.org/10.1007/978-

emg3d/surveys.py

@@ -717,8 +717,14 @@ def _rec_types_coord(self, source):
     def isfinite(self):
         """Return indices of the finite data."""
         if not hasattr(self, '_isfinite'):
-            self._isfinite = np.isfinite(self.data.observed.data)
-        return self._isfinite
+            finite = np.isfinite(self.data.observed.data)
+            # Only set the attribute if there is any data.
+            # Otherwise, this was called before observations were added.
+            if finite.sum() > 0:
+                self._isfinite = finite
+        else:
+            finite = self._isfinite
+        return finite
 
     def finite_data(self, data='observed'):
         """Return finite elements of selected `data`."""

tests/test_surveys.py

@@ -266,16 +266,23 @@ def test_add_noise(self):
         )
 
         data = np.logspace(0, -20, offs.size)+1j*np.logspace(0, -20, offs.size)
+        data = data[None, :, None]
 
         survey = surveys.Survey(
             sources=emg3d.electrodes.TxElectricDipole((0, 0, 0, 0, 0)),
             receivers=rec,
             frequencies=1.0,
-            data=data,
             relative_error=0.01,
             noise_floor=1e-15
         )
 
+        assert survey.isfinite.sum() == 0
+        assert not hasattr(survey, '_isfinite')
+        survey.data['observed'] = survey.data.observed.copy(data=data)
+        assert survey.isfinite.sum() == 21
+        assert hasattr(survey, '_isfinite')
+        assert survey.finite_data().shape == (21,)
+
         # Defined cutting
         survey.add_noise(min_offset=1000, min_amplitude=1e-19, add_to='test1')
         # Ensure short offsets are NaN
@@ -284,8 +291,6 @@ def test_add_noise(self):
         assert np.all(np.isnan(survey.data.test1.data[:, -1:, :]))
         # Ensure no others are none
         assert np.sum(np.isnan(survey.data.test1.data)) == 3
-        assert survey.isfinite.sum() == 21
-        assert survey.finite_data().shape == (21,)
 
         # No cutting
         survey.add_noise(min_offset=0, min_amplitude=10e-50, add_to='test2')