QBETA

qbeta
The beta inverse distribution function

         x = qbeta(p,a,b)
	Input	p	probability
		a,b	positive reals, parameters of the beta distribution
		(p,a,b  can be scalar or matrix with common size)

	Output		for each element of p, F is an ``inverse'' of the 
			beta cumulative distribution function with parameter
			a and b (the beta density is :
			x--> x.^(a-1) .* (1-x).^(b-1) ./ beta(a,b)1_{0<x<1})