betaln (MATLAB Functions)

Logarithm of beta function

Syntax

```
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

x = 510
betaln(x,x)

ans = 
      -708.8616

-708.8616 is slightly less than log(realmin). Computing beta(x,x) directly would underflow (or be denormal).

Algorithm

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

See Also

beta, betainc, gammaln

betainc bicg