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

scipy.special.betaln(a, b, out=None) = <ufunc 'betaln'>#

Natural logarithm of absolute value of beta function.

Computes ln(abs(beta(a, b))).

Parameters:

a, barray_like

Positive, real-valued parameters

outndarray, optional

Optional output array for function values

Returns:

scalar or ndarray

Value of the betaln function

See also

gamma

the gamma function

betainc

the regularized incomplete beta function

beta

the beta function

Examples

import numpy as np from scipy.special import betaln, beta

Verify that, for moderate values of a and b, betaln(a, b)is the same as log(beta(a, b)):

betaln(3, 4) -4.0943445622221

np.log(beta(3, 4)) -4.0943445622221

In the following beta(a, b) underflows to 0, so we can’t compute the logarithm of the actual value.

a = 400 b = 900 beta(a, b) 0.0

We can compute the logarithm of beta(a, b) by using betaln:

betaln(a, b) -804.3069951764146