Returns nans for eai_exp and aai_agg when exposures is empty

Author: luseverin

climada/engine/impact_calc.py

@@ -273,9 +273,13 @@ def _return_empty(self, save_mat):
         Impact or ImpactForecast
             Empty impact object with correct array sizes.
         """
+        if isinstance(self.hazard, HazardForecast):
+            eai_exp = np.nan * np.ones(self.n_exp_pnt)
+            aai_agg = np.nan
+        else:
+            eai_exp = np.zeros(self.n_exp_pnt)
+            aai_agg = 0.0
         at_event = np.zeros(self.n_events)
-        eai_exp = np.zeros(self.n_exp_pnt)
-        aai_agg = 0.0
         if save_mat:
             imp_mat = sparse.csr_matrix(
                 (self.n_events, self.n_exp_pnt), dtype=np.float64

climada/engine/test/test_impact_calc.py

@@ -51,8 +51,7 @@
 
 
 @pytest.fixture(autouse=True)
-def exposure_fixture():
-    n_exp = 50
+def exposure_fixture(n_exp=50):
     lats = np.linspace(-10, 10, n_exp)
     lons = np.linspace(-10, 10, n_exp)
     data = gpd.GeoDataFrame(
@@ -749,6 +748,15 @@ def test_impact_forecast_blocked_nonsense_attrs(
         assert np.all(np.isnan(impact.eai_exp))
         assert impact.eai_exp.shape == (len(exposure_fixture.gdf),)
 
+        # test that aai_agg and eai_exp are also nan when 0-size exp
+        empty_exp = exposure_fixture(n_exp=0)
+        impact_empty = ImpactCalc(
+            exposure_fixture, impact_func_set_fixture, hazard_forecast_fixture
+        ).impact(assign_centroids=True, save_mat=True)
+        assert np.isnan(impact_empty.aai_agg)
+        assert np.all(np.isnan(impact_empty.eai_exp))
+        assert impact_empty.eai_exp.shape == (len(empty_exp.gdf),)
+
 
 class TestImpactMatrixCalc(unittest.TestCase):
     """Verify the computation of the impact matrix"""