How to sort groups within sorted groups?

dplyr, group-by, r, sorting

Solution

By default, `group_by` has `add = FALSE`, which means rather than adding the second level of grouping, you are overwriting the first, leading to your error.

You could use:

library(dplyr)
a_table %>% group_by(grp1) %>%
            mutate(frst_count = n()) %>%
            group_by(grp2, add = TRUE) %>%
            mutate(scnd_count = n()) %>%
            arrange(frst_count, scnd_count)

Problem

There is this extra bit of complications on dplyr functionality that I haven't been able to solve. Mainly, I want to sort a second group within an already sorted group. So I have this data.frame: ``` a_table <- data.frame(id=1:30, grp1 = sample(LETTERS[1:5], 30, replace=TRUE, prob=c(1,1,2,2,3)), grp2 = sample(letters[6:8], 30, replace=TRUE, prob=c(2,2,3))) ``` I first group by `grp1` count the entries and order them, then for each `grp1` I count the values of each `grp2` and order them. My attempt to do this: ``` a_summary <- a_table %>% group_by(grp1) %>% mutate(frst_count = n()) %>% arrange(desc(frst_count)) %>% group_by(grp2) %>% mutate(scnd_count = n()) %>% arrange(desc(scnd_count)) ``` But there's obviously something missing because there's no group `summarise` and therefore no group sorting. Other tries with `summarise` haven't distinguished the group 1 and 2. Thanks.

Original source