Avoid redundant calls to np.unique in Impact.impact_at_reg (#848)

Author: peanutfun

CHANGELOG.md

@@ -47,6 +47,7 @@ Removed:
 - In the TropCyclone class in the Holland model 2008 and 2010 implementation, a doublecounting of translational velocity is removed [#833](https://github.com/CLIMADA-project/climada_python/pull/833)
 - `climada.util.test.test_finance` and `climada.test.test_engine` updated to recent input data from worldbank [#841](https://github.com/CLIMADA-project/climada_python/pull/841)
 - Set `nodefaults` in Conda environment specs because `defaults` are not compatible with conda-forge [#845](https://github.com/CLIMADA-project/climada_python/pull/845)
+- Avoid redundant calls to `np.unique` in `Impact.impact_at_reg` [#848](https://github.com/CLIMADA-project/climada_python/pull/848)
 
 ### Deprecated
 

climada/engine/impact.py

@@ -451,12 +451,12 @@ def impact_at_reg(self, agg_regions=None):
         at_reg_event = np.hstack(
             [
                 self.imp_mat[:, np.where(agg_regions == reg)[0]].sum(1)
-                for reg in np.unique(agg_reg_unique)
+                for reg in agg_reg_unique
             ]
         )
 
         at_reg_event = pd.DataFrame(
-            at_reg_event, columns=np.unique(agg_reg_unique), index=self.event_id
+            at_reg_event, columns=agg_reg_unique, index=self.event_id
         )
 
         return at_reg_event