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bundles / scipy latest / scipy / stats / _stats_py / zscore

function

scipy.stats._stats_py:zscore

source: /scipy/stats/_stats_py.py :2677

Signature

def   zscore ( a ,  axis = 0 ,  ddof = 0 ,  nan_policy = propagate )

Summary

Compute the z score.

Extended Summary

Compute the z score of each value in the sample, relative to the sample mean and standard deviation.

Parameters

a : array_like

An array like object containing the sample data.

axis : int or None, optional

Axis along which to operate. Default is 0. If None, compute over the whole array a.

ddof : int, optional

Degrees of freedom correction in the calculation of the standard deviation. Default is 0.

nan_policy : {'propagate', 'raise', 'omit'}, optional

Defines how to handle when input contains nan. 'propagate' returns nan, 'raise' throws an error, 'omit' performs the calculations ignoring nan values. Default is 'propagate'. Note that when the value is 'omit', nans in the input also propagate to the output, but they do not affect the z-scores computed for the non-nan values.

Returns

zscore : array_like

The z-scores, standardized by mean and standard deviation of input array a.

Notes

This function preserves ndarray subclasses, and works also with matrices and masked arrays (it uses asanyarray instead of asarray for parameters).

Array API Standard Support

zscore 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                   ✅                     ✅                   
Dask                  ✅                     n/a                 
====================  ====================  ====================

See dev-arrayapi for more information.

Examples

import numpy as np
a = np.array([ 0.7972,  0.0767,  0.4383,  0.7866,  0.8091,
               0.1954,  0.6307,  0.6599,  0.1065,  0.0508])
from scipy import stats
✓
stats.zscore(a)
✗
Computing along a specified axis, using n-1 degrees of freedom (``ddof=1``) to calculate the standard deviation: 
b = np.array([[ 0.3148,  0.0478,  0.6243,  0.4608],
              [ 0.7149,  0.0775,  0.6072,  0.9656],
              [ 0.6341,  0.1403,  0.9759,  0.4064],
              [ 0.5918,  0.6948,  0.904 ,  0.3721],
              [ 0.0921,  0.2481,  0.1188,  0.1366]])
✓
stats.zscore(b, axis=1, ddof=1)
✗
An example with ``nan_policy='omit'``: 
x = np.array([[25.11, 30.10, np.nan, 32.02, 43.15],
              [14.95, 16.06, 121.25, 94.35, 29.81]])
✓
stats.zscore(x, axis=1, nan_policy='omit')
✗

See also

numpy.mean

Arithmetic average

numpy.std

Arithmetic standard deviation

scipy.stats.gzscore

Geometric standard score

Aliases

  • scipy.stats.zscore

Referenced by

This package