Cube.aggregated_by() fails when derived coordinates are present #3637
Description
Hi, I've encountered the following bug(?) while working with files that contain derived coordinates:
import iris
import numpy as np
path = iris.sample_data_path('hybrid_height.nc')
cube = iris.load(path)[0]
aux_coord = iris.coords.AuxCoord(np.arange(cube.shape[1]) % 7,
long_name='random aux coord')
cube.add_aux_coord(aux_coord, 1)
cube.aggregated_by('random aux coord', iris.analysis.MEAN) # failsfails with
Traceback (most recent call last):
File "bug_derived_coord.py", line 9, in <module>
cube.aggregated_by('random aux coord', iris.analysis.MEAN)
File "miniconda3/envs/test/lib/python3.7/site-packages/iris/cube.py", line 3506, in aggregated_by
self.coord_dims(coord))
File "miniconda3/envs/test/lib/python3.7/site-packages/iris/cube.py", line 965, in add_aux_coord
raise ValueError('Duplicate coordinates are not permitted.')
ValueError: Duplicate coordinates are not permitted.
If the derived coordinate and the coordinate used for aggregation do not share a common dimension, it works:
import iris
import numpy as np
path = iris.sample_data_path('hybrid_height.nc')
cube = iris.load(path)[0]
cube = iris.util.new_axis(cube)
cube.add_aux_coord(iris.coords.AuxCoord(0, long_name='random aux coord'), 0)
cube = cube.aggregated_by('random aux coord', iris.analysis.MEAN) # does not failIf I remove the derived coordinate before the aggregation, it doesn't fail, too:
import iris
import numpy as np
path = iris.sample_data_path('hybrid_height.nc')
cube = iris.load(path)[0]
aux_coord = iris.coords.AuxCoord(np.arange(cube.shape[1]) % 7,
long_name='random aux coord')
cube.add_aux_coord(aux_coord, 1)
for aux_factory in cube.aux_factories:
cube.remove_aux_factory(aux_factory)
cube = cube.aggregated_by('random aux coord', iris.analysis.MEAN) # does not fail
print(cube)correctly prints
air_potential_temperature / (K) (model_level_number: 15; -- : 7; grid_longitude: 100)
Dimension coordinates:
model_level_number x - -
grid_longitude - - x
Auxiliary coordinates:
atmosphere_hybrid_height_coordinate x - -
sigma x - -
grid_latitude - x -
random aux coord - x -
surface_altitude - x x
Scalar coordinates:
forecast_period: 0.0 hours
forecast_reference_time: 2009-09-09 17:10:00
time: 2009-09-09 17:10:00
Attributes:
Conventions: CF-1.5
STASH: m01s00i004
source: Data from Met Office Unified Model 7.04
Cell methods:
mean: unknown
Thus, regular multidimensional coordinates that share dimensions with the aggregated coordinate (in this case surface_altitude) are also not a problem.
If this this is not a bug, a more precise error message would be nice. Thanks for your help!