Previous IDL Analyst Reference Guide: Special Functions Next

IMSL_LNBETA

Syntax | Return Value | Arguments | Keywords | Discussion | Example | Errors | Version History

The IMSL_LNBETA function evaluates the logarithm of the real beta function ln b(x, y).


Note
This routine requires an IDL Analyst license. For more information, contact your ITT Visual Information Solutions sales or technical support representative.

Syntax

Result = IMSL_LNBETA(x, y [, /DOUBLE])

Return Value

The value of the logarithm of the beta function b(x, y).

Arguments

x

First argument of the beta function. It must be positive.

y

Second argument of the beta function. It must be positive.

Keywords

DOUBLE

If present and nonzero, double precision is used.

Discussion

The beta function, b(x, y), is defined as:

and IMSL_LNBETA returns ln b(x, y). The logarithm of the beta function requires that x > 0 and y > 0. It can overflow for very large parameters.

Example

Evaluate the log of the beta function ln b (0.5, 0.2). 

PM, IMSL_LNBETA(.5, .2)  
      1.83556

Errors

Warning Errors

MATH_X_IS_TOO_CLOSE_TO_NEG_1—Result is accurate to less than one precision because the expression –x / (x + y) is too close to –1.

Version History

6.4
Introduced

  IDL Online Help (March 06, 2007)