[Numpy-discussion] 2-D Histogram

[josef.pktd at gmail.com]

On Tue, Sep 10, 2013 at 9:59 AM, Andreas Hilboll <lists at hilboll.de> wrote:
> On 10.09.2013 15:52, David Reed wrote:
>> Hi there,
>>
>> Is there a faster way to perform a 2D Histogram from a 2D matrix than
>> what I have below:
>>
>> def spatial_histogram(frame, n_bins):
>> shape = frame.shape
>>
>> h_len = shape[0]/n_bins
>> w_len = shape[1]/n_bins
>>
>> h_ind = range(0, shape[0], h_len)
>> w_ind = range(0, shape[1], w_len)
>>
>> max_val = 255*h_len*w_len
>>
>> out = np.empty((n_bins, n_bins), np.uint8)
>>
>> for ii in range(n_bins):
>> for jj in range(n_bins):
>> out[ii, jj] = np.sum(frame[h_ind[ii]:h_ind[ii]+h_len,
>> w_ind[jj]:w_ind[jj]+w_len])/max_val*255
>>
>> return out
>>
>> Should I try implementing this in Cython, or is there something I can do
>> in Numpy?
>>
>> Thanks!
>
> David,
>
> are you aware of Scipy's binne_statistic_2d method?
>
>
> http://docs.scipy.org/doc/scipy/reference/generated/scipy.stats.binned_statistic_2d.html

That's modeled after numpy.histogram2d, and just calculates other
statistics besides histogram

Josef

>
> At first glance it can do what you're trying to do.
>
> Andreas.
>
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