Group aggregate has wrong (and different than getitem!) behavior for groups from other axes

>>> arr = ndtest("a=a0,a2,a1")
>>> arr
a  a0  a2  a1
    0   1   2
>>> g = arr.a.i[1]
>>> g
a.i[1]
>>> arr[g]
1
>>> arr.sum(g)
1

Now let us define another array with the same axis name, and reuse the g group:

>>> arr2 = ndtest("a=a0..a2")
>>> arr2
a  a0  a1  a2
    0   1   2

For getitem, the group is retargeted to the "local array" axis (i.e. arr2.a) by using the labels corresponding to the group on the original axis:

>>> arr2[g]
2

But for group aggregates, this is the position, irrespective of the label:

>>> arr2.sum(g)
1

This is because of the:

axis_key = axis_key.with_axis(real_axis)

line in AxisCollection._guess_axis which should probably use retarget_to instead.

In fact, the problem caused by that line is present for LGroup too (but there only for slice groups):

>>> arr = ndtest(3)
>>> arr
a  a0  a1  a2
    0   1   2
>>> a2 = Axis('a=a0,a2,a1')
>>> arr.sum(arr.a['a0:a1'])
1
>>> arr.sum(a2['a0:a1']) # should be 3
1

And in fact, I just noticed I had already found and fixed this bug in one of my local branches (slice_groups_incompatible_axis) almost two years ago. Pffff... 😭

I am not 100% sure we should have this retarget behavior in the first place. Both can be confusing. But I am 100% sure getitem and group aggregate should behave the same.

yvda stumbled on this one too.

There is probably also a problem in _group_aggregate:

groups = tuple(g.with_axis(axis) for g in groups)

In fact, I should search for all places where with_axis is used. Unsure any use makes sense.

FIX: fixed array[slice_group_from_an_incompatible_axis] (fixes larray…

FIX: fixed array[slice_group_from_an_incompatible_axis] (fixes #1146 …

fixed by #1149

Since it modifies behavior (and some models actually rely on it -- I wonder if the occurences I found are bugs in the models or not), I only added a warning, will turn that to an error in 0.36 and only change the behavior in 0.37 or possibly later for users who skip releases 😞

FIX: do not change buggy behavior users rely on yet (see #1117 and #1146

Navigation Menu

Repository navigation

Group aggregate has wrong (and different than getitem!) behavior for groups from other axes #1117

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Group aggregate has wrong (and different than getitem!) behavior for groups from other axes #1117

Description

Activity

gdementen commented on Oct 2, 2024

gdementen commented on Nov 17, 2025

gdementen commented on Nov 17, 2025

gdementen commented on Dec 5, 2025

gdementen commented on Dec 18, 2025

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions