concatenate data frame

hi all

Here is a small part of my code:

tab_tmp<-tab[1:(no[off_set[i-1]+1]+(no[off_set[i]+1]-no[off_set[i-1]+1])),length(tab)];

tab_tmp1<-tab[(no[off_set[i-1]+1]+(no[off_set[i]+1]-no[off_set[i-1]+1])):length(TotalFillTimeHours),length(tab)];

tab<-c(tab_tmp,tab_tmp1);
attach(tab);

Here is the output:
Error in attach(tab) : attach only works for lists and data frames
Execution halted


How do i concatenate them in order to keep the data frame structure?


thks for your help
guillaume