如何在已排序的组中对组进行排序? [英] How to sort groups within sorted groups?

问题描述

我无法解决dplyr功能的其他一些复杂问题.主要是，我想对已经排序的组中的第二个组进行排序.

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.

所以我有这个data.frame:

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))) 

我首先用grp1分组，对条目进行计数并对其进行排序，然后对于每个grp1，我对每个grp2的值进行计数并对其进行排序.

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.

我尝试这样做:

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))

但是显然缺少一些东西，因为没有组summarise，因此也没有组排序.其他使用summarise的尝试没有区分组1和2.

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.

谢谢.

推荐答案

默认情况下，group_by具有add = FALSE，这意味着您不添加第二级分组，而是覆盖了第一级分组，从而导致错误.

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.

您可以使用:

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)

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