Calculate the incomplete Gamma function (lower)
Calculate the CEPHES function, igam, in the range [a > 0; x
> 0]. The function is defined by
igam(a,x) = 1/sqrt(a) Int_(0)^(x) 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.
Relative error:
| IEEE |
0,30 |
200000 |
3.6e-14 |
2.9e-15 |
| IEEE |
0,100 |
300000 |
9.9e-14 |
1.5e-14 |
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 the igam of a=1, x=2 .
sherpa> igam([1,2],[2,3])
Calculate the igam of a=[1,2], x=[2,3] .
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