how to use a variable in grepl function within a loop-R -

i new r and, have problems looping , grepl functions have data like:

str(peptidesfilter)   'data.frame':   78389 obs. of  130 variables:  $ sequence                      : chr  "aaaaaiggr" "aaaaaiggrpnyygneggr" "aaaaassnpgggpemvr" "aaaaavggr" ...  $ first.amino.acid              : chr  "a" "a" "a" "a" ...  $ protein.group.ids             : chr  "1" "1;2;4" "2;5 "3" "4;80" ... 

i want filter data according $ protein.group.ids using grepl function below

    peptidesfilter.new <- peptidesfilter[grepl('(^|;)2($|;)', peptidesfilter$protein.group.ids),] 

i want loop every individual data ( e.g 1, 2, 3, etc...) , re-write name of data frame containing variable peptidesfilter.i

   =1    while( <= n) { peptidesfilter.[[i]] <-     peptidesfilter[grepl('(^|;)i($|;)',    peptidesfilter$protein.group.ids),]      i=i+1 } 

i have 2 problems, main 1 in grep1 function not recognized variable , how can re-name filtered data in way contain variable.

any ideas?

for grepl problem can use paste0 example:

paste0('(^|;)',i,'($|;)') 

for loop , can :

ll <- lapply(seq(1:4),function(x)          peptidesfilter[grepl(paste0('(^|;)',x,'($|;)'),                            peptidesfilter$protein.group.ids),]) 

then can transform data.frame:

do.call(rbind,ll)              sequence first.amino.acid protein.group.ids 1            aaaaaiggr                                1 2  aaaaaiggrpnyygneggr                            1;2;4 21 aaaaaiggrpnyygneggr                            1;2;4 3    aaaaassnpgggpemvr                              2;5 4            aaaaavggr                                3 22 aaaaaiggrpnyygneggr                            1;2;4