Calculate the compliment of the incomplete Gamma function (upper)
Calculate the CEPHES function, igamc, in the range [a > 0;
x > 0]. The function is defined as
The function, igamc, is defined by
igamc(a,x) = 1 - igam(a,x)
= 1/sqrt(a) Int_(x)^(Inf) e^(-t) t^(a-1) dt
In this implementation, both arguments must be positive.
The integral is evaluated by either a power series or
continued fraction expansion, depending on the relative
values of a and x. Arguments can be in scalar or array form.
Tested at random a, x.
a x Relative error:
| IEEE |
0.5,100 |
0,100 |
200000 |
1.9e-14 |
1.7e-15 |
| IEEE |
0.01,0.5 |
0,100 |
200000 |
1.4e-13 |
1.6e-15 |
Cephes Math Library Release 2.0: April, 1987.
Copyright 1985, 1987 by Stephen L. Moshier.
Direct inquiries to 30 Frost Street, Cambridge, MA 02140.
Calculate igamc with a=1, x=2.
sherpa> igamc([1,2],[2,3]);
Calculate igamc with a=[1,2], x=[2,3] .
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