Rui pointed out that you can examine the source yourself. FAQ 7.40 has a link to an article with detail on finding and examining the source code.
A general algorithm for checking for duplicates follows (I have not examined to R source code to see if they use something more clever). Create an empty object (I will call it seen). This could be a simple vector, but for efficiency it is better to use an object type that has fast lookup, e.g. binary tree, associative array/hash/dictionary, etc. Create an empty vector of logicals the same length as x (I will call it result). loop from 1 to the length of x (or from the length to 1 if fromLast=TRUE), on each iteration check to see if the value of x[i] is in seen If it is: set result[i] to TRUE If it is not: add the current value to seen and set result[i] to false After the loop finishes, throw away seen and reclaim the memory, then return result. Since it looks like you are using this on a matrix or data frame, there is probably a preprocessing step that combines all the values on each row into a single character string. On Tue, Aug 4, 2020 at 6:45 AM K Purna Prakash <prakash.n...@gmail.com> wrote: > > Dear Sir(s), > I request you to provide the detailed* internal mathematical working > mechanism of the following function *for better understanding. > *x[duplicated(x) | duplicated(x, fromLast=TRUE), ]* > I am having some confusion in understanding how duplicates are being > identified when thousands of records are there. > I will look for a positive response. > Thank you, > K.Purna Prakash. > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > 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. -- Gregory (Greg) L. Snow Ph.D. 538...@gmail.com ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
