Add margin row totals in dplyr chain

Question

I would like to add overall summary rows while also calculating summaries by group using dplyr. I have found various questions asking how to do this, e.g. here, here, and he

Answer 1

One option is with do

mtcars %>%
   count(cyl, gear) %>%
   ungroup() %>% 
   mutate(cyl=as.character(cyl)) %>% 
   do(bind_rows(., data.frame(cyl="Total", count(mtcars, gear)))) 
   #or replace the last 'do' step with 
   #bind_rows(cbind(cyl='Total', count(mtcars, gear))) #from  @JonnyPolonsky's comments

#      cyl  gear     n
#     
#1      4     3     1
#2      4     4     8
#3      4     5     2
#4      6     3     2
#5      6     4     4
#6      6     5     1
#7      8     3    12
#8      8     5     2
#9  Total     3    15
#10 Total     4    12
#11 Total     5     5