[R] Removing variables from data frame with a wile card

[Andrew Simmons]

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 <styen using 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"...
>
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