Evaluates the real incomplete beta function Ix = βx (a, b)/β(a, b).
Synopsis
#include <imsls.h>
float imsls_f_beta_incomplete (float x, float a, float b)
The type double procedure is imsls_d_beta_incomplete.
Required Arguments
float x
(Input)
Point at which the incomplete beta function is to be evaluated.
float a
(Input)
Point at which the incomplete beta function is to be evaluated.
float b
(Input)
Point at which the incomplete beta function is to be evaluated.
Return Value
The value of the incomplete beta function.
Description
The incomplete beta function is defined to be
The incomplete beta function requires that 0 ≤ x ≤ 1, a > 0, and b > 0. It underflows for sufficiently small x and large a. This underflow is not reported as an error. Instead, the value zero is returned.
Example
Evaluate the log of the incomplete beta function I0.61 =β0.61 (2.2,3.7)/β(2.2,3.7).
#include <imsls.h>
int main()
{
float x = 0.61;
float a = 2.2;
float b = 3.7;
float ans;
ans = imsls_f_beta_incomplete(x, a, b);
printf("beta incomplete = %f\n", ans);
}
beta incomplete = 0.8822;
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