Hi > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-bounces@r- > project.org] On Behalf Of Jie > Sent: Monday, March 11, 2013 2:24 AM > To: r-help > Subject: [R] How to obtain the original indices of elements after > sorting > > Dear All, > > Suppose I have a vector X = (x_1, x_2, ...., x_n), X_sort = sort(X) = > (x_(1), x_(2), ... , x(n) ), and I would like to know the original > position of these ordered x_(i) in X, how can I do it? > > case 1: all values are unique > x <- c( 3, 5, 4, 6) > x.sort <- sort(x) #
That is why order is included. > x <- c( 3, 5, 4, 6) > order(x) [1] 1 3 2 4 > I believe that it is mentioned in sort help page. Regards Petr > # I would like to obtain a vector (1, 3, 2, 4) which indicates that 3 > in x is still the 1st element in x.sort, 5 is at the 3rd position in > x.sort. etc. > > case 2: some x_i's have the same value > x <- c(3, 3, 5, 5, 4, 4, 6, 6) > I would like to obtain a vector as (1, 2, 5, 6, 3, 4, 7, 8) > > I do not want to use which and loop over the vector to do it since for > a long vector it is not fast enough. > Thank you for your suggestion. > > Best wishes, > Jie > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting- > guide.html > and provide commented, minimal, self-contained, reproducible code. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
