0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 ibeta(a, b, z) z a = 9, b = 1 a = 7, b = 2 a = 5, b = 5 a = 2, b = 7 a = 1, b = 9 ibeta