Thanks Therneau, duplicated() function works well. --- Kai On Friday, September 10, 2021, 05:13:47 AM PDT, Therneau, Terry M., Ph.D. <thern...@mayo.edu> wrote: I prefer the duplicated() function, since the final code will be clear to a future reader. (Particularly when I am that future reader).
last <- !duplicated(mydata$ID, fromLast=TRUE) # point to the last ID for each subject mydata$data3[last] <- NA Terry T. (I read the list once a day in digest form, so am always a late reply.) On 9/10/21 5:00 AM, r-help-requ...@r-project.org wrote: > Hello List, > Please look at the sample data frame below: > > ID date1 date2 date3 > 1 2015-10-08 2015-12-17 2015-07-23 > > 2 2016-01-16 NA 2015-10-08 > 3 2016-08-01 NA 2017-01-10 > 3 2017-01-10 NA 2016-01-16 > 4 2016-01-19 2016-02-24 2016-08-01 > 5 2016-03-01 2016-03-10 2016-01-19 > This data frame was sorted by ID and date1. I need to set the column date3 as > missing for the "last" record for each ID. In the sample data set, the ID 1, > 2, 4 and 5 has one row only, so they can be consider as first and last > records. the data3 can be set as missing. But the ID 3 has 2 rows. Since I > sorted the data by ID and date1, the ID=3 and date1=2017-01-10 should be the > last record only. I need to set date3=NA for this row only. > > the question is, how can I identify the "last" record and set it as NA in > date3 column. > Thank you, > Kai > [[alternative HTML version deleted]] > [[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.