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

[Steven T. Yen]

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"...