
igamma - incomplete Gamma function

Calling sequence:
igamma(x, y)

Parameter:

x, y   --  expressions

Summary:

The incomplete Gamma function is defined as

    igamma(x, y) = int( exp(-t) * t^(x-1), t=y..infinity )

At the moment, numerical calculation is only available for positive real numbers.

igamma(x, 0) is equivalent to gamma(x).  igamma returns the function call
with evaluated arguments, if the argument cannot be evaluated to a number.
igamma is a kernel function.

>>  igamma(2,4);

     exp(- 4) 5

>>  igamma(2.0,4);

      0.9157819444e-1

See also:  gamma

