LNBETA Function
Evaluates the logarithm of the real beta function ln β(x, y).
Usage
result = LNBETA(x, y)
Input Parameter
x—Point at which the logarithm of the beta function is to be evaluated. x must be positive.
y—Point at which the logarithm of the beta function is to be evaluated. y must be positive.
Returned Value
result—The value of the logarithm of the beta function β(x, y).
Input Keywords
Double—If present and nonzero, double precision is used.
Discussion
The beta function, β(x, y), is defined to be:
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 arguments.
Example
Evaluate the log of the beta function ln β(0.5, 0.2).
x = 0.5
y = 0.2
ans = LNBETA(x, y)
PRINT, 'log beta(', x, ',', y, ') =', ans; PV-WAVE prints: log beta( 0.500000, 0.200000) = 1.83556
Warning Errors
STAT_X_IS_TOO_CLOSE_TO_NEG_1—The result is accurate to less than one precision because the expression −x/(x + y) is too close to −1.
