The IMSL_BETAI function evaluates the real incomplete beta function.

This routine requires an IDL Advanced Math and Stats license. For more information, contact your sales or technical support representative.

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, I0.61(2.2, 3.7) is computed and printed.

PM, IMSL_BETAI(.61, 2.2, 3.7)
  0.882172

Syntax

Result = IMSL_BETAI(X, A, B[, /DOUBLE])

Return Value

The value of the incomplete beta function.

Arguments

X

Upper limit of integration.

A

First beta distribution parameter.

B

Second beta distribution parameter.

Keywords

DOUBLE (optional)

If present and nonzero, double precision is used.

Version History

6.4

Introduced

See Also

IMSL_BETA, IMSL_BETACDF