a^k e^-a / k! with k! replaced by k^k e^-k sqrt(2 pi k), beside the
exact pmf.
Arguments
- k
event count, >= 1.
- a
expected count, > 0.
Value
list(approx, exact, rel_error).
References
Morin, D. J. (2016). Probability: For the Enthusiastic
Beginner. Createspace. Eq (5.16).
Examples
PoisStirl(10, 8)$rel_error
#> [1] 0.008365359
