
{{alias}}( x, a, b[, regularized[, upper]] )
    Computes the regularized incomplete beta function.

    The `regularized` and `upper` parameters specify whether to evaluate the
    non-regularized and/or upper incomplete beta functions, respectively.

    If provided `x < 0` or `x > 1`, the function returns `NaN`.

    If provided `a < 0` or `b < 0`, the function returns `NaN`.

    If provided `NaN` as any argument, the function returns `NaN`.

    Parameters
    ----------
    x: number
        First function parameter.

    a: number
        Second function parameter.

    b: number
        Third function parameter.

    regularized: boolean (optional)
        Boolean indicating whether the function should evaluate the regularized
        or non-regularized incomplete beta function. Default: `true`.

    upper: boolean (optional)
        Boolean indicating whether the function should return the upper tail of
        the incomplete beta function. Default: `false`.

    Returns
    -------
    y: number
        Function value.

    Examples
    --------
    > var y = {{alias}}( 0.5, 2.0, 2.0 )
    0.5
    > y = {{alias}}( 0.5, 2.0, 2.0, false )
    ~0.083
    > y = {{alias}}( 0.2, 1.0, 2.0 )
    0.36
    > y = {{alias}}( 0.2, 1.0, 2.0, true, true )
    0.64
    > y = {{alias}}( NaN, 1.0, 1.0 )
    NaN
    > y = {{alias}}( 0.8, NaN, 1.0 )
    NaN
    > y = {{alias}}( 0.8, 1.0, NaN )
    NaN
    > y = {{alias}}( 1.5, 1.0, 1.0 )
    NaN
    > y = {{alias}}( -0.5, 1.0, 1.0 )
    NaN
    > y = {{alias}}( 0.5, -2.0, 2.0 )
    NaN
    > y = {{alias}}( 0.5, 2.0, -2.0 )
    NaN

    See Also
    --------

