8000 np.count_nonzero() should accept axis parameter · Issue #391 · numpy/numpy · GitHub
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kernc opened this issue Aug 27, 2012 · 9 comments
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np.count_nonzero() should accept axis parameter #391

kernc opened this issue Aug 27, 2012 · 9 comments
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01 - Enhancement component: numpy._core

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@kernc
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kernc commented Aug 27, 2012

Currently, np.count_nonzero() accepts only the input array. I propose adding axis parameter similar to that of functions np.sum() and np.max() etc.

>>> A = np.arange(6).reshape(2,3)
>>> np.count_nonzero(A)  # with axis=None, count_nonzero in flattened A
5
>>> np.count_nonzero(A, axis=0)
array([1, 2, 2])
>>> np.count_nonzero(A, axis=1)
array([2, 3])

I think the alternative (A != 0).sum(axis=rows_or_cols) isn't as clear.
@numpy-gitbot numpy-gitbot mentioned this issue Oct 19, 2012
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@charris
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charris commented Feb 17, 2014

Sounds reasonable.

@jaimefrio
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I wrote this elsewhere, but if no one else wants to try it, I can go on an "add axis" spree: I have working code for bincount (will try to make it into a PR tonight), and have searchsorted, interp, and now count_nonzero in the pipeline. Is there any other obvious one I am forgetting about?

@herr-biber
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Any news on this? I'd be interested in this feature as well.

@juliantaylor
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an alternative might be to try and adapt sum(bool) to use the much faster non-casting count_nonzero code.
sum is already a full ufunc with all bells and whistles so one gets (extended) axis for free

@seberg
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seberg commented Apr 23, 2014

I am unsure if the ufunc reduce supports mixed type inner loops.

@WarrenWeckesser
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+1 for adding an axis argument to count_nonzero().

@JaimieMurdock
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+1 here as well.

@tentrillion
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Also +1 here.

@lzkelley
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+1

This was referenced Jan 29, 2016
Closed
Merged 736F
@shoyer shoyer closed this as completed in 0fc9e45 Aug 5, 2016
luyahan pushed a commit to plctlab/numpy that referenced this issue Apr 25, 2024
@howjmay
Merge pull request numpy#391 from howjmay/vmaxv
a1055f9 
feat: Add vmaxv[q]_[s8|s16|s32|u8|u16|u32|f32|f64]
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@seberg @charris @WarrenWeckesser @juliantaylor @JaimieMurdock @kernc @herr-biber @jaimefrio @lzkelley @tentrillion
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