Stirling2: Compute Stirling numbers of the second kind
Description
This function computes Stirling numbers of the second kind, \(S(n,
k)\), which count the number of ways of partitioning n distinct
objects in to k non-empty sets.
Usage
Stirling2(n, k)
S2(n, k)
Value
An vector of Stirling numbers of the second kind
Arguments
n
A vector of one or more positive integers
k
A vector of one or more positive integers
Functions
S2(): Compute Stirling numbers of the second kind
Author
James Curran
Details
The implementation on this function is a simple recurrence relation which
defines $$S(n, k) = kS(n - 1, k), + S(n - 1, k - 1)$$ for \(k > 0\)
with the inital conditions \(S(0, 0) = 1\) and \(S(n, 0) = S(0, n) =
0\). If n and n have different lengths then expand.grid
is used to construct a vector of (n, k) pairs