I think what's happening is the process by which you make your list: I assume that before you run this loop, you write: varmat <- list() So, when you run the loop, each time you do the command varmat <- list(varmat, var), you make a new list whose first element is a list of lists ("varmat") and the second element is your vcov matrix. This will lead to a pretty confusing data object. Here's a simpler way to make your list: varmat <- list() for (i in 1:whatever){ var <- vcov(out[i]) varmat[[i]] <- var } Or if you want to go the apply route, assuming that you can make "out" a list of regressions: varmat <- lapply(out, function(x) vcov(x)) -Michael On Apr 8, 2010, at 9:30 AM, Carly Knight wrote: > Hi Michael, > > Thanks! I did try the [[x]] notation. I may be missing something but > I still can't the result to be a matrix (and it has to be a matrix > object to be fed into the other function). This is the code I am > getting: > > var1<- varmat[[1]] > > is.matrix(var1) > [1] FALSE > > > > as.matrix(var1) > [,1] > [1,] List,2 > [2,] ? > > > > I'm probably missing something simple but do you know what I am > doing wrong? > > > > > On Thu, Apr 8, 2010 at 9:20 AM, Michael Barnett > <mlbarnett at gmail.com> wrote: > Carly - > > To properly index a list element, you need to type "[[x]]", not > "[x]", so if you use varmat[[1]], that will return the first element > of the list as a matrix object. > > -Michael > > On Apr 8, 2010, at 9:18 AM, Carly Knight wrote: > >> Hey everyone, >> >> I have a question not related to the problem set. For the >> replication I have created a loop to run through a bunch of my >> regressions. I've stored all the variance-covariance matrices in a >> list object. Now that I have them, I want to extract each matrix to >> put into my mvrnormal() funciton. however, I can't seem to turn it >> back into a matrix. I've tried unlisting, calling a specific >> element of the list, and everytime I try to do this or apply >> as.matrix() I end up getting an error or something odd. This is the >> code I am working with. Does anyone know how to properly unlist? >> >> } >> >> >> My code to try to unlist: >> x<-as.matrix(unlist(lapply(varmat, t))[1]) >> >> I've also tried: >> unlist(varmat[1]) >> unlist(varmat)[1] >> >> Any help would be very much appreciated! >> >> - Carly >> >> >> -- >> Carly Knight >> Ph.D. Student >> Department of Sociology >> Harvard University >> Phone: (281) 682-4063 >> E-Mail: crknight at fas.harvard.edu >> _______________________________________________ >> gov2001-l mailing list >> gov2001-l at lists.fas.harvard.edu >> http://lists.fas.harvard.edu/mailman/listinfo/gov2001-l > > > _______________________________________________ > gov2001-l mailing list > gov2001-l at lists.fas.harvard.edu > http://lists.fas.harvard.edu/mailman/listinfo/gov2001-l > > > > > -- > Carly Knight > Ph.D. Student > Department of Sociology > Harvard University > Phone: (281) 682-4063 > E-Mail: crknight at fas.harvard.edu > _______________________________________________ > gov2001-l mailing list > gov2001-l at lists.fas.harvard.edu > http://lists.fas.harvard.edu/mailman/listinfo/gov2001-l