scipy.ndimage.

histogram#

scipy.ndimage.histogram(input, min, max, bins, labels=None, index=None)[source]#

Calculate the histogram of the values of an array, optionally at labels.

Histogram calculates the frequency of values in an array within bins determined by min, max, and bins. The labels and index keywords can limit the scope of the histogram to specified sub-regions within the array.

Parameters:

inputarray_like: Data for which to calculate histogram.
min, maxint: Minimum and maximum values of range of histogram bins.
binsint: Number of bins.
labelsarray_like, optional: Labels for objects in input. If not None, must be same shape as input.
indexint or sequence of ints, optional: Label or labels for which to calculate histogram. If None, all values where label is greater than zero are used

Returns:

histndarray: Histogram counts.

Examples

>>> import numpy as np
>>> a = np.array([[ 0.    ,  0.2146,  0.5962,  0.    ],
...               [ 0.    ,  0.7778,  0.    ,  0.    ],
...               [ 0.    ,  0.    ,  0.    ,  0.    ],
...               [ 0.    ,  0.    ,  0.7181,  0.2787],
...               [ 0.    ,  0.    ,  0.6573,  0.3094]])
>>> from scipy import ndimage
>>> ndimage.histogram(a, 0, 1, 10)
array([13,  0,  2,  1,  0,  1,  1,  2,  0,  0])

With labels and no indices, non-zero elements are counted:

>>> lbl, nlbl = ndimage.label(a)
>>> ndimage.histogram(a, 0, 1, 10, lbl)
array([0, 0, 2, 1, 0, 1, 1, 2, 0, 0])

Indices can be used to count only certain objects:

>>> ndimage.histogram(a, 0, 1, 10, lbl, 2)
array([0, 0, 1, 1, 0, 0, 1, 1, 0, 0])