Incomplete Beta Function

ibeta(a, x, y) Returns the value of the incomplete beta function of x and y with parameter a.

Arguments:

• a is a real scalar between 0 and 1, inclusive.
• x, y are real positive scalars.

Notes:

• For any valid x and y, ibeta(1,x,y) = 1, that is, the function becomes complete at a = 1. The definition is related to the Γ function.
• The incomplete beta function arises often in probabilistic applications. For example, the cumulative probability density for the Student's t and binomial distributions can be computed in terms of ibeta.