I would like to group data and then arrange the table so that groups with the highest values are shown first. E.g. in mtcars dataset, I would like to group the cars by number of cylinders and then arrange the table so that the groups with the highest mean mpg are shown first
mtcars %>% group_by (cyl) %>% arrange (desc(mean (mpg)))
this produces an error:
Error: incorrect size (1) at position 1, expecting : 32
the reason I am asking is that filter() when applied after group_by() is applied to the whole group, not individual rows.
Perhaps this? First, group by cyl, then fill a new column with mean(mpg), which you can then arrange by however you want, and finally remove the temporary mean(mpg) column.
mtcars %>%
group_by(cyl) %>%
mutate(mean_mpg = mean(mpg)) %>%
arrange(desc(mean_mpg)) %>%
select(-mean_mpg)
#> # A tibble: 32 x 11
#> # Groups: cyl [3]
#> mpg cyl disp hp drat wt qsec vs am gear carb
#> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl>
#> 1 22.8 4 108 93 3.85 2.32 18.6 1 1 4 1
#> 2 24.4 4 147. 62 3.69 3.19 20 1 0 4 2
#> 3 22.8 4 141. 95 3.92 3.15 22.9 1 0 4 2
#> 4 32.4 4 78.7 66 4.08 2.2 19.5 1 1 4 1
#> 5 30.4 4 75.7 52 4.93 1.62 18.5 1 1 4 2
#> 6 33.9 4 71.1 65 4.22 1.84 19.9 1 1 4 1
#> 7 21.5 4 120. 97 3.7 2.46 20.0 1 0 3 1
#> 8 27.3 4 79 66 4.08 1.94 18.9 1 1 4 1
#> 9 26 4 120. 91 4.43 2.14 16.7 0 1 5 2
#> 10 30.4 4 95.1 113 3.77 1.51 16.9 1 1 5 2
#> # ... with 22 more rows