## Function Poisson-Cdf

(

**poisson-cdf** < k > < x > )

Computes the cumulative distribution function for a Poisson random variable

with mean ` x' evaluated at `

k.' The result is the probability that the number of

Poisson random events occurring will be between 0 and k-1 inclusive, if the

expected number is ` x.' The argument `

k' should be an integer, while `x' should

be a float. The implementation follows Numerical Recipes in C, section 6.2