The column should be row-binded. With Matrix dimensions being n x k, n should be length of the column and k should be numbers of data frames (and therefore length of the list, I guess). I am trying an approach with a separate function now:
extractwisp <- function(x){
x <- x[,4]
}
wisp <- as.matrix(lapply(ok_list, extractwisp))
I'm checking now if that works.