BETAINC Incomplete Beta Function

Usage

Computes the incomplete beta function. The betainc function takes 3 or 4 arguments

  A = betainc(X,Y,Z)

  A = betainc(X,Y,Z,tail)

where X is either a float or double array with elements in [0,1] interval, Y and Z are real non-negative arrays. tail specifies the tail of the incomplete beta function. If tail is 'lower' (default) than the integral from 0 to x is computed. If tail is 'upper' than the integral from x to 1 is computed. All arrays must be the same size or be scalar. The output vector A is the same size (and type) as input arrays.

Function Internals

The incomplete beta function is defined by the integral:

Example

Here is a plot of the betainc function over the range [.2,.8].

--> x=.2:.01:.8;
--> y = betainc(x,5,3);
--> plot(x,y); xlabel('x'); ylabel('betainc(x,5,3)');

which results in the following plot.