Hello R users, I am dealing with some resonably big data sets that I have split up into lists based on various factors. In the code below, I have got my code producing 100 values between point1x and point1y for the first matrix in my list. for (k in 1:length(point1x[[1]][, 1])) { linex[[k]] = seq(point1x[[1]][, 1][k], point2x[[1]][, 1][k], length = 100)} This works properly when I specify point1x[[1]] and point2x[[1]], but I need to repeat this process for point1x[[2]]... point1x[[j]] and append it within another list. Perhaps something along the lines of this, for (j in 1:length(something)) { for (k in 1:length(point1x[[j]][, 1])) { linex[[j]][[k]] = seq(point1x[[j]][, 1][k], point2x[[j]][, 1][k], length = 100)}} But, R wont let me do this, so, my question is, how can I produce lists within lists in R using a similar code to above? I could do this manually by changing the values of n and then setting up the list using biglist[[1]] = linex #for n=1 biglist[[2]] = linex #for n=2 etc I can then call to lists within the list using biglist[[1]][[4]] etc, but I need to automate all of this. Am I missing something basic with respect to list structures? Thanks again, Darcy.