Fix multi variable indices (fixes #208)

.flake8

+[flake8]
+max-line-length = 88
+extend-ignore = E203

CHANGELOG.md

@@ -22,20 +22,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [0.13.1] - 2020-10-21
 
-### Added
-
-### Changed
-
-### Deprecated
-
-### Removed
-
 ### Fixed
 
 - Rename percentile_occurrence index function (fixes #202)
 
-### Security
-
 
 ## [0.13.0] - 2020-10-19
 

climix/iris.py

@@ -107,6 +107,12 @@ def multicube_aggregated_by(cubes, coords, aggregator, **kwargs):
             lambda groupby_slice:
                 ref_cube[front_slice + (groupby_slice,) + back_slice],
             groupby.group(),)
+
+        def agg(cube):
+            data = data_getter(cube)
+            result = aggregate(data,
+                               axis=dimension_to_groupby, cube=cube, **kwargs)
+            return result
     else:
         groupby_subcubes = map(
             lambda groupby_slice: {
@@ -116,11 +122,12 @@ def multicube_aggregated_by(cubes, coords, aggregator, **kwargs):
             groupby.group(),
         )
 
-    def agg(cube):
-        data = data_getter(cube)
-        result = aggregate(data,
-                           axis=dimension_to_groupby, cube=cube, **kwargs)
-        return result
+        def agg(cubes):
+            data = {argname: data_getter(cube) for argname, cube in cubes.items()}
+            result = aggregate(data,
+                               axis=dimension_to_groupby, cube=cubes, **kwargs)
+            return result
+
     result = list(map(agg, groupby_subcubes))
     aggregateby_data = stack(result, axis=dimension_to_groupby)