Evaluates the logarithm of the real beta function ln β(x, y).

x—First argument of the beta function. It must be positive.

y—Second argument of the beta function. It must be positive.

result—The value of the logarithm of the beta function β(x, y).

Double—If present and nonzero, double precision is used.

The beta function, β(x, y), is defined as:

and LNBETA returns ln β(x, y). The logarithm of the beta function requires that x > 0 and y > 0. It can overflow for very large parameters.

Evaluate the log of the beta function ln β (0.5, 0.2).

PM, LNBETA(.5, .2) ; PV-WAVE prints: 1.83556

MATH_X_IS_TOO_CLOSE_TO_NEG_1—Result is accurate to less than one precision because the expression –x / (x + y) is too close to –1.