Steven, The default is drop=TRUE.
If you want to retain a data.frame and not have it reduced to a vector under some circumstances. https://win-vector.com/2018/02/27/r-tip-use-drop-false-with-data-frames/ -----Original Message----- From: R-help <r-help-boun...@r-project.org> On Behalf Of Steven T. Yen Sent: Sunday, February 12, 2023 5:19 PM To: Andrew Simmons <akwsi...@gmail.com> Cc: R-help Mailing List <r-help@r-project.org> Subject: Re: [R] Removing variables from data frame with a wile card In the line suggested by Andrew Simmons, mydata <- mydata[, !grepl("^yr", colnames(mydata)), drop = FALSE] what does drop=FALSE do? Thanks. On 1/14/2023 8:48 PM, Steven Yen wrote: > Thanks to all. Very helpful. > > Steven from iPhone > >> On Jan 14, 2023, at 3:08 PM, Andrew Simmons <akwsi...@gmail.com> wrote: >> >> You'll want to use grep() or grepl(). By default, grep() uses >> extended regular expressions to find matches, but you can also use >> perl regular expressions and globbing (after converting to a regular >> expression). >> For example: >> >> grepl("^yr", colnames(mydata)) >> >> will tell you which 'colnames' start with "yr". If you'd rather you >> use globbing: >> >> grepl(glob2rx("yr*"), colnames(mydata)) >> >> Then you might write something like this to remove the columns >> starting with yr: >> >> mydata <- mydata[, !grepl("^yr", colnames(mydata)), drop = FALSE] >> >> On Sat, Jan 14, 2023 at 1:56 AM Steven T. Yen <st...@ntu.edu.tw> wrote: >>> >>> I have a data frame containing variables "yr3",...,"yr28". >>> >>> How do I remove them with a wild card----something similar to "del yr*" >>> in Windows/doc? Thank you. >>> >>>> colnames(mydata) >>> [1] "year" "weight" "confeduc" "confothr" "college" >>> [6] ... >>> [41] "yr3" "yr4" "yr5" "yr6" "yr7" >>> [46] "yr8" "yr9" "yr10" "yr11" "yr12" >>> [51] "yr13" "yr14" "yr15" "yr16" "yr17" >>> [56] "yr18" "yr19" "yr20" "yr21" "yr22" >>> [61] "yr23" "yr24" "yr25" "yr26" "yr27" >>> [66] "yr28"... >>> >>> ______________________________________________ >>> 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. [[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. ______________________________________________ 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.
