Inverse of incomplete beta function¶

incbi(a, b, y)¶

Given y, the function finds x such that incbet(a, b, y) = x.

Parameters:	a (float) – a positive number b (float) – a positive number x (float) – any number within [0, 1]

Description¶

The routine performs interval halving or Newton iterations to find the root of incbet(a,b,x) - y = 0.

				relative error
	x	a, b
arithmetic	domain	domain	# trials	peak	rms
IEEE	0, 1	.5, 10000	50000	5.8e-12	1.3e-13
IEEE	0, 1	.25, 100	100000	1.8e-13	3.9e-15
IEEE	0, 1	0, 5	50000	1.1e-12	5.5e-15
VAX	0, 1	.5, 100	25000	3.5e-14	1.1e-15
With a and b constrained to half-integer or integer values
IEEE	0, 1	.5, 10000	50000	5.8e-12	1.1e-13
IEEE	0, 1	.5, 100	100000	1.7e-14	7.9e-16
With a=.5, b constrained to half-integer or integer values
IEEE	0, 1	.5, 10000	10000	8.3e-11	1.0e-11