Evaluates the logarithm of the real beta function ln β(x, y).
Synopsis
#include <imsls.h>
float imsls_f_log_beta (float x, float y)
The type double procedure is imsls_d_log_beta.
Required Arguments
float x
(Input)
Point at which the logarithm of the beta function is to be evaluated.
It must be positive.
float y
(Input)
Point at which the logarithm of the beta function is to be evaluated.
It must be positive.
Return Value
The value of the logarithm of the beta function β(x, y).
Description
The beta function, β(x, y), is defined to be
and imsls_f_log_beta 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.
Warning Errors
IMSLS_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.
Example
Evaluate the log of the beta function ln β(0.5, 0.2).
#include <imsls.h>
int main()
{
float x = 0.5;
float y = 0.2;
float ans;
ans = imsls_f_log_beta(x, y);
printf("log beta(%f,%f) = %f\n", x, y, ans);
}
Output
log beta(0.500000,0.200000) = 1.835562
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