`scipy.ndimage._measurements:histogram`

source: /scipy/ndimage/_measurements.py :1559

Signature

   def     histogram (    input    ,    min    ,    max    ,    bins    ,    labels    =  None   ,    index    =  None     )

Summary

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

Extended Summary

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

input : array_like: Data for which to calculate histogram.
min, max : int: Minimum and maximum values of range of histogram bins.
bins : int: Number of bins.
labels : array_like, optional: Labels for objects in input. If not None, must be same shape as input.
index : int 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

hist : ndarray: Histogram counts.

Notes

Array API Standard Support

histogram has experimental support for Python Array API Standard compatible backends in addition to NumPy. Please consider testing these features by setting an environment variable SCIPY_ARRAY_API=1 and providing CuPy, PyTorch, JAX, or Dask arrays as array arguments. The following combinations of backend and device (or other capability) are supported.

====================  ====================  ====================
Library               CPU                   GPU
====================  ====================  ====================
NumPy                 ✅                     n/a                 
CuPy                  n/a                   ✅                   
PyTorch               ✅                     ⛔                   
JAX                   ⚠️ no JIT             ⛔                   
Dask                  ⚠️ computes graph     n/a                 
====================  ====================  ====================

See dev-arrayapi for more information.

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)

✓

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

lbl, nlbl = ndimage.label(a)
ndimage.histogram(a, 0, 1, 10, lbl)

✓

Indices can be used to count only certain objects:

ndimage.histogram(a, 0, 1, 10, lbl, 2)

✓

Aliases

scipy.ndimage.histogram