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

[Steven Yen]

Thanks to all. Very helpful.

Steven from iPhone

> On Jan 14, 2023, at 3:08 PM, Andrew Simmons <akwsimmo using 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 <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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