fast subsetting in R

Question

I\'ve got a dataframe dat of size 30000 x 50. I also have a separate list that contains points to groupings of rows from this dataframe, e.g.,

rows <- list(c(         


        

Answer 1

You could try this modification:

system.time(lapply(rows, function(r) {dat[ rownames(dat) %in% r, ]}))