I found the following message maybe help. And I will try it. Hi there, I have just found that the ``attach'' function can get you into trouble when called many times. For example, you have a simulation routine called ``f()'', in which you used ``attach'' and no corresponding ``detach''. Then you call this function many times. You will find that the system performance get slower and slower, because you are making the R search path longer and longer. So be careful when you use attach in a function! Below is a demonstration of this performance loss, you will see a linear growth in CPU time usage. Adding a ``detach()'' call at the end of ``f'' will get rid of this problem. ############################### f <- function(){ theta <- list(one=2.0, two=0.3, three=0.4) attach(theta) x <- c(one, two, three) sample(x, 1) } test <- function(n=400){ timeu <- numeric(n) for(i in seq(n)){ timeu[i] <- system.time({ resi <- f() })[3] } plot(timeu) } test() ############################## -- Sincerely, Changbin -- [[alternative HTML version deleted]]