Expose histogram bin estimators?

[dstansby]

Would it be possible to expose the histogram bin estimators available in numpy? e.g.

numpy/numpy/lib/function_base.py

Line 393 in e94ed84

def _hist_bin_auto(x):

and others.

We would find it useful in Matplotlib for computing bins without having to spend time computing the full histogram (xref matplotlib/matplotlib#8636)

[eric-wieser]

Is the application here:

• Compute the bins for np.concatenate([a, b, c])
• Compute the histogram for each of a, b, c, using those bins?

That seems like a pretty reasonable application to me. I'm not sure if we should directly expose those functions, or just expose a bins_only=True argument to np.histogram.

[eric-wieser]

I'm not sure how we can expose the uniform range optimization in that use case, but I suppose optimality is not the primary concern.

[eric-wieser]

It's waiting on #10186, but I have a local patch that exposes bin_edges = histogram_bins(a, bins=10, range=None, weights).

Does that sound like a reasonable API?

[dstansby]

I think the application is computing bins for np.concatenate([a,b,c]). All of your suggestions above sound good!

[shoyer]

I like the separate histogram_bins function.

[eric-wieser]

Alright, as of #10261 this is now trivial to patch on master in np.lib.histograms as

def histogram_bin_edges(a, bins=10, range=None, weights=None):
    a, weights = _ravel_and_check_weights(a, weights)
    bin_edges, _ = _histogram_bins(a, bins, range, weights)
    return bin_edges

Most of the work here is to add a docstring, and some simple tests - so tagging as an easy fix

I suppose emailing the mailing list to confirm the function name could be valuable too.

[kirit93]

Does this issue still need to be worked on? If so, I'd like to work on this!

[eric-wieser]

@kirit93: Go for it!

[kirit93]

@eric-wieser Have you added this function to master?

    a, weights = _ravel_and_check_weights(a, weights)
    bin_edges, _ = _histogram_bins(a, bins, range, weights)
    return bin_edges

There's no function _histogram_bins in np.lib.histograms.

Shouldn't the function be

def histogram_bin_edges(a, bins=10, range=None, weights=None):
    a, weights = _ravel_and_check_weights(a, weights)
    bin_edges, _ = _get_bin_edges(a, bins, range, weights)
    return bin_edges

I just need to add this function to np.lib.histogram with a docstring and add a test for this in np.lib.tests.test_histograms right?

Thanks!

[eric-wieser]

@dstansby: This will be in 1.15 - although matplotlib's minimum numpy version is currently 8 minor versions behind that, so you could be waiting a long time!

I suppose you could backport the np.lib.histograms module in its entirety?