The zelig() and setx() functions are working fine for me but I am having trouble with the sim() command. I get the following error: Error in mvrnorm(num, mu = coef(object), Sigma = vcov(object)) : incompatible arguments I am running a negative binomial model with a large number of covariates (about 300) and a large data set (about 150,000 observations). I would be interested in bootstrapping as an alternative, but I need a way to bootstrap with smaller subsets of my dataset or I run out of memory, and I am not sure how to do this either. Running R version 2.15.0. Using Zelig (Version 3.5.5, built: 2010-01-20) Thanks! ________________________________ Mr. Louis Merlin, AICP Doctoral Student UNC CH Department of City and Regional Planning