BETA Function

Evaluates the real beta function b(x, y).

Usage

result = BETA(x, y)

Input Parameters

x—First beta parameter. It must be positive.

y—Second beta parameter. It must be positive.

Returned Value

result—The value of the beta function b(x, y). If no result can be computed, then NaN (Not a Number) is returned.

Input Keywords

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

Discussion

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

 

requiring that x > 0 and y > 0. It underflows for large parameters.

Example

Plot the beta function over [e, 1/4 + e] × [e, 1/4 + e] for e = 0.01. The results are shown in Real Beta Function Plot.

x = 1e-2 + .25 * FINDGEN(25)/24

y = x

b = FLTARR(25, 25)

; Compute values of the beta function.

FOR i=0L, 24 DO b(i, *) = BETA(x(i), y)

; Plot the computed values as a surface and rotate the plot.

SURFACE, b, x, y, XTitle = 'X', YTitle = 'Y', Az = 320, ZAxis = 2

Real Beta Function Plot

Alert Errors

MATH_BETA_UNDERFLOW—Parameters must not be so large that the result underflows.

Fatal Errors

MATH_ZERO_ARG_OVERFLOW—One of the parameters is so close to zero that the result overflows.