Using the "join" function from the plyr package preserves the data order library(plyr) join(grades2, info, by="grade", type="left", match="all")
Nilesh -----Original Message----- From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of Dimitri Liakhovitski Sent: Wednesday, March 08, 2017 12:45 PM To: Jeff Newmiller <jdnew...@dcn.davis.ca.us> Cc: r-help <r-help@r-project.org> Subject: Re: [R] Why is merge sorting even when sort = F? I understood your answer. The point is that sort = TRUE that doesn't sort is plain confusing. Instead, the option should have been something like efficient = TRUE or FALSE. At least then no one would stupidly expect sort = TRUE to sort and sort = FALSE to NOT sort. On Wed, Mar 8, 2017 at 12:51 PM, Jeff Newmiller <jdnew...@dcn.davis.ca.us> wrote: > If you are still wondering, try re-reading my answer. FALSE is more > efficient, TRUE is sorted. Lack of sorting has nothing to do with preserving > order. > -- > Sent from my phone. Please excuse my brevity. > > On March 8, 2017 8:55:06 AM PST, Dimitri Liakhovitski > <dimitri.liakhovit...@gmail.com> wrote: >>Thank you. I was just curious what sort=FALSE had no impact. >>Wondering what it is there for then... >> >>On Wed, Mar 8, 2017 at 11:43 AM, Jeff Newmiller >><jdnew...@dcn.davis.ca.us> wrote: >>> Merging is not necessarily an order-preserving operation, but >>> sorting >>can make the operation more efficient. The sort=TRUE argument forces >>the result to be sorted, but sort=FALSE is in not a promise that order >>will be preserved. (I think the imperfect sorting occurs when there >>are multiple keys but am not sure.) You can add columns to the input >>data that let you restore some semblance of the original ordering >>afterward, or you can roll your own possibly-less-efficient merge >>using match and >>indexing: >>> >>> info[ match( grades2$grade, info$grade ), ] >>> -- >>> Sent from my phone. Please excuse my brevity. >>> >>> On March 8, 2017 8:07:27 AM PST, Dimitri Liakhovitski >><dimitri.liakhovit...@gmail.com> wrote: >>>>Hello! >>>>I have a vector 'grades' and a data frame 'info': >>>> >>>>grades2 <- data.frame(grade = c(1,2,2,3,1)) info <- data.frame( >>>> grade = 3:1, >>>> desc = c("Excellent", "Good", "Poor"), >>>> fail = c(F, F, T) >>>>) >>>> >>>>I want to get the info for all grades I have in info: >>>> >>>>This solution resorts everything in the order of column 'grade': >>>>merge(grades2, info, by = "grade", all.x = T, all.y = F) >>>> >>>>Could you please explain why this solution also resorts - despite >>sort >>>>= FALSE? >>>>merge(grades2, info, by = "grade", all.x = T, all.y = F, sort = >>FALSE) >>>> >>>>Thanks a lot! -- Dimitri Liakhovitski ______________________________________________ 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. This email and any attachments were sent from a Monsanto email account and may contain confidential and/or privileged information. If you are not the intended recipient, please contact the sender and delete this email and any attachments immediately. Any unauthorized use, including disclosing, printing, storing, copying or distributing this email, is prohibited. All emails and attachments sent to or from Monsanto email accounts may be subject to monitoring, reading, and archiving by Monsanto, including its affiliates and subsidiaries, as permitted by applicable law. Thank you. ______________________________________________ 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.
