8000 np.ma.masked_where(copy=False) fails to modify array in place when there were no masked elements in the array initially · Issue #18946 · numpy/numpy · GitHub
[go: up one dir, main page]
Skip to content

np.ma.masked_where(copy=False) fails to modify array in place when there were no masked elements in the array initially #18946

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom
Closed
jacekt opened this issue May 8, 2021 · 1 comment · Fixed by #18967
Closed

np.ma.masked_where(copy=False) fails to modify array in place when there were no masked elements in the array initially #18946

jacekt opened this issue May 8, 2021 · 1 comment · Fixed by #18967
Labels
00 - Bug component: numpy.ma masked arrays
Milestone
1.21.0 release

Comments

@jacekt
Copy link
jacekt commented May 8, 2021 •
edited by rgommers
Loading

ma.masked_where documentation says that:

copy : bool
    If True (default) make a copy of `a` in the result.  If False modify
    `a` in place and return a view.

But it fails to modify the array's mask when the original mask is empty:

Reproducing code example:

>>> import numpy as np
>>> import numpy.ma as ma

>>> a = ma.array([1, 2, 3, 4])
>>> a
masked_array(data=[1, 2, 3, 4],
             mask=False,
       fill_value=999999)

>>> ma.masked_where(a==3, a, copy=False)
masked_array(data=[1, 2, --, 4],
             mask=[False, False,  True, False],
       fill_value=999999)

>>> a
masked_array(data=[1, 2, 3, 4],
             mask=False,
       fill_value=999999)

It works properly when there are some masked elements in the array already:

>>> a = ma.array([1, 2, 3, 4], mask=[1, 0, 0, 0])
>>> a
masked_array(data=[--, 2, 3, 4],
             mask=[ True, False, False, False],
       fill_value=999999)

>>> ma.masked_where(a==3, a, copy=False)
masked_array(data=[--, 2, --, 4],
             mask=[ True, False,  True, False],
       fill_value=999999)

>>> a
masked_array(data=[--, 2, --, 4],
             mask=[ True, False,  True, False],
       fill_value=999999)

Error message:

None.

NumPy/Python version information:

1.20.2 3.8.6 (tags/v3.8.6:db45529, Sep 23 2020, 15:52:53) [MSC v.1927 64 bit (AMD64)]
numpy-1.20.2-cp38-cp38-win_amd64.whl
@jacekt jacekt changed the title np.ma.masked_where(copy=False) fails to modify array in place when there are no masked elements in the array np.ma.masked_where(copy=False) fails to modify array in place when there were no masked elements in the array initially May 9, 2021
@constanzafierro constanzafierro mentioned this issue May 9, 2021
Merged
@rgommers rgommers added this to the 1.21.0 release milestone May 10, 2021
rgommers pushed a commit that referenced this issue May 10, 2021
@constanzafierro
BUG: fix np.ma.masked_where(copy=False) when input has no mask (#18967)
b6eb3d8 
Fixes gh-18946
@rgommers
Copy link
Member

Thanks for the report @jacekt. Fixed now.

pbrod pushed a commit to pbrod/numpy that referenced this issue May 11, 2021
@constanzafierro @pbrod
BUG: fix np.ma.masked_where(copy=False) when input has no mask (numpy…
2a42ccb 
…#18967)

Fixes numpygh-18946
@QuLogic QuLogic mentioned this issue Jun 24, 2021
Closed
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
< 4930 !-- -->
Assignees
No one assigned
Labels
00 - Bug component: numpy.ma masked arrays
Projects
None yet
Milestone
1.21.0 release
Development

Successfully merging a pull request may close this issue.

BUG: fix np.ma.masked_where(copy=False) when input has no mask constanzafierro/numpy
2 participants
@rgommers @jacekt
0