# Documentation

### This is machine translation

Translated by
Mouseover text to see original. Click the button below to return to the English verison of the page.

To view all translated materals including this page, select Japan from the country navigator on the bottom of this page.

# betaln

Logarithm of beta function

L = betaln(Z,W)

## Description

L = betaln(Z,W) computes the natural logarithm of the beta function log(beta(Z,W)), for corresponding elements of arrays Z and W, without computing beta(Z,W). Since the beta function can range over very large or very small values, its logarithm is sometimes more useful.

Z and W must be real and nonnegative. They must be the same size, or either can be scalar.

## Examples

collapse all

Compute the natural logarithm of the beta function according to the value of X without directly computing the beta function. beta(X,X) results in floating point arithmetic underflow.

X = 510;
betaln(X,X)
ans = -708.8616

## Algorithms

betaln(z,w) = gammaln(z)+gammaln(w)-gammaln(z+w)