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!
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_stati... At first glance it can do what you're trying to do. Andreas.
On Tue, Sep 10, 2013 at 9:59 AM, Andreas Hilboll <lists@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_stati...
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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