betaln - 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
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