Using grepl in R -

in cases these 2 different ways of implimentation give different results?

data(mtcars) firstway <- mtcars[grepl('6',mtcars$cyl),] secondway <- mtcars[mtcars$cyl=='6',] 

if these ways give same results of them recommended , why? thanks

using package microbenchmark, can see faster

library(microbenchmark) m <- microbenchmark(mtcars[grepl('6',mtcars$cyl),], mtcars[mtcars$cyl=='6',], times=10000)      unit: microseconds                          expr     min      lq     mean  median      uq      max neval  mtcars[grepl("6", mtcars$cyl), ] 229.080 234.738 247.5324 236.693 239.417 6713.914 10000       mtcars[mtcars$cyl == "6", ] 214.902 220.210 231.0240 221.956 224.471 7759.507 10000 

it looks == faster, when possible should use that

however, functions not same thing. grepl searches if string present @ wheras == checks whether expressions equal

grepl("6", mtcars$disp)   [1]  true  true false false  true false  true  true false  true  true false false false false  true false [18] false false false false false false false false false false false false false false false  mtcars$disp == "6"  [1] false false false false false false false false false false false false false false false false false [18] false false false false false false false false false false false false false false false