Leonard Mada
2021-Sep-14 13:46 UTC
[R] Fastest way to extract rows of smaller matrix many times by index to make larger matrix? and multiply columsn of matrix by vector
Hello Nevil, you could test something like: # the Matrix m = matrix(1:1000, ncol=10) m = t(m) # Extract Data idcol = sample(seq(100), 100, TRUE); # now columns for(i in 1:100) { ??? m2 = m[ , idcol]; } m2 = t(m2); # transpose back It may be faster, although I did not benchmark it. There may be more complex variants. Maybe it is warranted to try for 10^7 extractions: - e.g. extracting one row and replacing all occurrences of that row; Sincerely, Leonard ======= It seems I cannot extract digested mail anymore. I hope though that the message is processed properly.