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

An addition to @arkrun's answer that is not easy to add as a comment:

Although a little more complex, this format allows for previous modifications in the data frame. Useful when there is a longer chain of verbs before the table is generated. (You want to change names, or select only specific variables)

mtcars %>%
   count(cyl, gear) %>%
   ungroup() %>% 
   mutate(cyl=as.character(cyl))
bind_rows(group_by(.,gear) %>%
              summarise(n=sum(n)) %>%
              mutate(cyl='Total')) %>%
spread(cyl)

## A tibble: 3 x 5
#   gear   `4`   `6`   `8` Total
#*     
#1     3     1     2    12    15
#2     4     8     4     0    12
#3     5     2     1     2     5

This can also be doubled up to generate a total row for the spread as well.

mtcars %>%
  count(cyl, gear) %>%
  ungroup() %>% 
  mutate(cyl=as.character(cyl),
         gear = as.character(gear)) %>%
  bind_rows(group_by(.,gear) %>%
              summarise(n=sum(n)) %>%
              mutate(cyl='Total')) %>%
  bind_rows(group_by(.,cyl) %>%
              summarise(n=sum(n)) %>%
              mutate(gear='Total')) %>%
  spread(cyl,n,fill=0)

# A tibble: 4 x 5
   gear   `4`   `6`   `8` Total
*     
1     3     1     2    12    15
2     4     8     4     0    12
3     5     2     1     2     5
4 Total    11     7    14    32