Dear all , I would like to extend a list structure to a structure that can hold much more date. Please find a small example of my code and my questions regarding it: lst <- list() for (k in c(1:mmax)){ # 1 ..max as the f.fxy gets as input order-1. for (l in c(1:nmax)){ sr[findCoord(c(i,j),sr)[1],findCoord(c(i,j),sr)[2]]<-fxy(c(i,j)) } } lst[[listcounter]] <-sr # Store the value inside lst listcounter<-listcounter+1 } } In the code above I was calculating the values of a matrix sr(200*200 matrix) and then I was storing the whole .matrix inside the list called lst (lst[[listcounter]]<-sr). This was used for one scenario. I would like to run the same but for 100 different scenarios (randomly created). Thus I want to extend lst to a double-list or a matrix that for every different out of the 100 scenarios stores everything. The ideal would be to have lst[[listcounter]][[scenario_index]]<-sr where scenario_index is the index for the current scenario (ranges from 1 to 100). Could you please explain me how I can do that in R? Regards Alex