[R] Sim function

[Noah Silverman]

I'm reading Gellman's book "Data Analysis Using Regression and 
Multilevel-Hierarchical Models"

In Chapter 7 (and later), he makes frequent referent to a function names 
"sim".

I can't find the function anywhere, not in my standard R install, or in 
any of the packages.

Doe anyone have a reference for this?

Thanks!