r - 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 here, but no clear solution. One possible approach is to perform count twice and bind the rows:

mtcars %>% 
  count(cyl, gear) %>% 
  bind_rows(
    count(mtcars, gear)
  )

which nearly produces what I need (the left-most column has NAs rather than 'Total' or similar):

     cyl  gear     n
   <dbl> <dbl> <int>
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     NA     3    15
10    NA     4    12
11    NA     5     5

Am I missing an easier/built-in solution?

Answer 1

With adorn_totals() from the janitor package:

library(janitor)
mtcars %>%
  tabyl(cyl, gear) %>%
  adorn_totals("row") 

   cyl  3  4 5
     4  1  8 2
     6  2  4 1
     8 12  0 2
 Total 15 12 5

To get from there to the "long" form in your post, add tidyr::gather() to the pipeline:

mtcars %>%
  tabyl(cyl, gear) %>%
  adorn_totals("row") %>%
  tidyr::gather(gear, n, 2:ncol(.), convert = TRUE)

     cyl gear  n
1      4    3  1
2      6    3  2
3      8    3 12
4  Total    3 15
5      4    4  8
6      6    4  4
7      8    4  0
8  Total    4 12
9      4    5  2
10     6    5  1
11     8    5  2
12 Total    5  5

Self-promotion alert, I authored this package - adding this answer b/c it's a genuinely efficient solution here.