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igamc
Complemented incomplete gamma integral.SYNOPSIS:
double a, x, y, igamc();
y = igamc(a, x);
DESCRIPTION:
The function is defined by
igamc(a,x) = 1 - igam(a,x)
inf.
-
1 | | -t a-1
= ----- | e t dt
- | |
| (a) -
x
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.
ACCURACY:
Tested at random a, x.
a x Relative error:
arithmetic domain domain # trials peak rms
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