BETAI Function

Evaluates the real incomplete beta function.

Usage

result = BETAI(x, a, b)

Input Parameters

x—Upper limit of integration.

a—First beta distribution parameter.

b—Second beta distribution parameter.

Returned Value

result—The value of the incomplete beta function.

Input Keywords

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

Discussion

The incomplete beta function is defined as:

 

requiring 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

In this example, I_0.61(2.2, 3.7) is computed and printed.

PM, BETAI(.61, 2.2, 3.7) ; PV-WAVE prints: 0.882172