`scipy.stats._stats_py:moment`

source: build-install/usr/lib/python3.14/site-packages/scipy/stats/_stats_py.py:1084

Signature

def moment(a, order = 1, axis = 0, nan_policy = propagate, *, center = None, keepdims = False)

Summary

Calculate the nth moment about the mean for a sample.

Extended Summary

A moment is a specific quantitative measure of the shape of a set of points. It is often used to calculate coefficients of skewness and kurtosis due to its close relationship with them.

Parameters

a : array_like

Input array.

order : int or 1-D array_like of ints, optional

Order of central moment that is returned. Default is 1.

axis : int or None, default: 0

If an int, the axis of the input along which to compute the statistic. The statistic of each axis-slice (e.g. row) of the input will appear in a corresponding element of the output. If None, the input will be raveled before computing the statistic.

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

Defines how to handle input NaNs.

propagate: if a NaN is present in the axis slice (e.g. row) along which the statistic is computed, the corresponding entry of the output will be NaN.
omit: NaNs will be omitted when performing the calculation. If insufficient data remains in the axis slice along which the statistic is computed, the corresponding entry of the output will be NaN.
raise: if a NaN is present, a ValueError will be raised.

nan_policy='raise' and nan_policy='omit' are not supported by lazy backends, and nan_policy='omit' is not compatible with MArray input. For multidimensional input, nan_policy='omit' is supported only by the NumPy backend. Instead, mask NaN values using MArray; and use the default nan_policy. See Notes for support information.

center : float or None, optional

The point about which moments are taken. This can be the sample mean, the origin, or any other be point. If None (default) compute the center as the sample mean.

keepdims : bool, default: False

If this is set to True, the axes which are reduced are left in the result as dimensions with size one. With this option, the result will broadcast correctly against the input array.

Returns

n-th moment about the `center` : ndarray or float: The appropriate moment along the given axis or over all values if axis is None. The denominator for the moment calculation is the number of observations, no degrees of freedom correction is done.

Notes

The k-th moment of a data sample is:

m_{k} = \frac{1}{n} i = 1 \sum n (x_{i} - c)^{k}

Where n is the number of samples, and c is the center around which the moment is calculated. This function uses exponentiation by squares ^[1] for efficiency.

Note that, if a is an empty array (a.size == 0), array moment with one element (moment.size == 1) is treated the same as scalar moment (np.isscalar(moment)). This might produce arrays of unexpected shape.

Beginning in SciPy 1.9, np.matrix inputs (not recommended for new code) are converted to np.ndarray before the calculation is performed. In this case, the output will be a scalar or np.ndarray of appropriate shape rather than a 2D np.matrix. Similarly, while masked elements of masked arrays are ignored, the output will be a scalar or np.ndarray rather than a masked array with mask=False.

Examples

from scipy.stats import moment

✓

moment([1, 2, 3, 4, 5], order=1)
moment([1, 2, 3, 4, 5], order=2)

✗

np.float64(2.0)

Aliases

scipy.stats.moment