Dear R-List member, I have a problem when I'm trying to save two arrays from a foreach-loop. I'm also not sure whether this is possible or just my inexperience. However, this works perferctly fine with a for-loop. Here is an example code - any help is much appreciated!!: ############ n.vpn = 2 n.run= 3 # create to empty matrices sme = matrix(NA,4,n.vpn) test = matrix(NA,4,n.vpn) # arrays to save the data from a nested (for) loop x = array(NA,dim=c(4,n.vpn,n.run)) y = array(NA,dim=c(4,n.vpn,n.run)) # function which returns two matrices saved in one list check <-function(n) { for(i in 1:n.vpn) { sme[,i] = c((1+i):(4+i)) test[,i]= c((5+i):(8+i)) } retval = list(sme=sme,test=test) return(retval) } # Call the check function multiple time and save every list entry into a specific arrays "x" and "y"; stop time system.time(for(j in 1:n.run) { z = check(j) x[,, j] <- z$sme y[,, j] <- z$test }) #### trying to do the same with a foreach loop - does not work!! require(doSMP) workers <- startWorkers(2) # My computer has 2 cores registerDoSMP(workers) notcreative = array(NA,dim=c(4,n.vpn,n.l?ufe)) tempList = list(matrix(NA,4,n.vpn),matrix(NA,4,n.vpn)) system.time(notcreative <- foreach(j=1:n.run) %dopar% { tempList=check(j) x[,,j] = tempList$sme y[,,j] = tempList$test }) stopWorkers(workers) -- ____________ lic. phil. Nicolas A. J. Berkowitsch Universit?t Basel Fakult?t f?r Psychologie Economic Psychology Missionsstrasse 62a CH-4055 Basel Tel. +41 61 267 05 75 E-Mail nicolas.berkowitsch at unibas.ch Web psycho.unibas.ch/abteilungen/abteilung-details/home/abteilung/economic-psychology