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Should coordmap composition check coordinate system names? #247
Description
At the moment, this gives an error:
import numpy as np
from nipy.core.api import CoordinateSystem, AffineTransform, compose
ijk = CoordinateSystem('ijk', 'voxel')
xyz = CoordinateSystem('xyz', 'world')
ijk_to_xyz = AffineTransform(ijk, xyz, np.eye(4))
pqr = CoordinateSystem('pqr', 'crazy')
ijk2 = CoordinateSystem('ijk', 'another_name')
pqr_to_ijk = AffineTransform(pqr, ijk2, np.eye(4))
pqr_to_xyz = compose(ijk_to_xyz, pqr_to_ijk)
The error is:
ValueError Traceback (most recent call last)
<ipython-input-23-42effb708f95> in <module>()
----> 1 pqr_to_xyz = compose(ijk_to_xyz, pqr_to_ijk)
/Users/mb312/usr/local/lib/python2.6/site-packages/nipy/core/reference/coordinate_map.pyc in compose(*cmaps)
1085 allaffine = np.all([isinstance(cmap, AffineTransform) for cmap in cmaps])
1086 if allaffine:
-> 1087 return _compose_affines(*cmaps)
1088 else:
1089 warnings.warn("composition of non-affine CoordinateMaps is "
/Users/mb312/usr/local/lib/python2.6/site-packages/nipy/core/reference/coordinate_map.pyc in _compose_affines(*affines)
1584 np.dot(cmap.affine, cur.affine))
1585 else:
-> 1586 raise ValueError("domains and ranges don't match up correctly")
1587 return cur
1588
ValueError: domains and ranges don't match up correctly
That is because the 'ijk' and 'ijk2' coordinate systems have the same axis names, but different coordinate names. I think we should probably only check the coordinate axis names, not the coordinate system name....
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