scipy.special.expit — SciPy v1.15.2 Manual (original) (raw)

scipy.special.expit(x, out=None) = <ufunc 'expit'>#

Expit (a.k.a. logistic sigmoid) ufunc for ndarrays.

The expit function, also known as the logistic sigmoid function, is defined as expit(x) = 1/(1+exp(-x)). It is the inverse of the logit function.

Parameters:

xndarray

The ndarray to apply expit to element-wise.

outndarray, optional

Optional output array for the function values

Returns:

scalar or ndarray

An ndarray of the same shape as x. Its entries are expit of the corresponding entry of x.

Notes

As a ufunc expit takes a number of optional keyword arguments. For more information see ufuncs

Added in version 0.10.0.

Examples

import numpy as np from scipy.special import expit, logit

expit([-np.inf, -1.5, 0, 1.5, np.inf]) array([ 0. , 0.18242552, 0.5 , 0.81757448, 1. ])

logit is the inverse of expit:

logit(expit([-2.5, 0, 3.1, 5.0])) array([-2.5, 0. , 3.1, 5. ])

Plot expit(x) for x in [-6, 6]:

import matplotlib.pyplot as plt x = np.linspace(-6, 6, 121) y = expit(x) plt.plot(x, y) plt.grid() plt.xlim(-6, 6) plt.xlabel('x') plt.title('expit(x)') plt.show()