6.8.15 The lower incomplete γ function: igamma
The lower incomplete γ function is defined by
The igamma command computes the lower incomplete γ
function.
-
igamma takes two mandatory arguments and one optional
argument:
-
a, a number.
- b, a positive real number.
- Optionally, the number 1.
- igamma(a,b) returns γ(a,b).
- igamma(a,b,1) returns a normalized version of the
function; namely γ(a,b)/Γ(a).
Examples.
-
Input:
igamma(4.0,3.0)
Output:
- Input:
igamma(4.0,3.0,1)
Output:
since Γ(4) = 6 and 2.11660866731/6 = 0.352768111218.