如何通过group_by的group-number对数据表进行数字/标签化？ [英] How to number/label data-table by group-number from group_by?

问题描述

我有一个tbl_df，我想对（u，v）观察到的每个不同的整数组合对group_by（u，v）进行分组。

I have a tbl_df where I want to group_by(u,v) for each distinct integer combination observed with (u,v).

编辑：这是通过在 group_indices（） / hadley / dplyr / releasesrel =nofollow noreferrer> dplyr 0.4.0

this was resolved by adding group_indices() back in dplyr 0.4.0

a）然后我想分配每个不同的组一些任意不同的数字label = 1,2,3 ...
eg组合（u，v）==（2,3）可以得到标签1，（1,3）可以得到2，依此类推。
如何使用一个 mutate（），没有三步骤总结和自我加入？

a) I then want to assign each distinct group some arbitrary distinct number label=1,2,3... e.g. the combination (u,v)==(2,3) could get label 1, (1,3) could get 2, and so on. How to do this with one mutate(), without a three-step summarize-and-self-join?

dplyr有一个整齐的函数 n（），但它给出了其组内的元素数量，而不是整体组号。 在 data.table 这将简单地称为 .GRP 。

dplyr has a neat function n(), but that gives the number of elements within its group, not the overall number of the group. In data.table this would simply be called .GRP.

b）其实我是什么真的要分配一个字符串/字符标签（'A'，'B'，...）。
但是通过整数编号是足够好的，因为我可以使用 integer_to_label（i）如下。除非有一个聪明的方法来合并这两个？但不要出汗这部分。

b) Actually what I really want to assign a string/character label ('A','B',...). But numbering groups by integers is good-enough, because I can then use integer_to_label(i) as below. Unless there's a clever way to merge these two? But don't sweat this part.

set.seed(1234)

# Helper fn for mapping integer 1..26 to character label
integer_to_label <- function(i) { substr("ABCDEFGHIJKLMNOPQRSTUVWXYZ",i,i) }

df <- tbl_df(data.frame(u=sample.int(3,10,replace=T), v=sample.int(4,10,replace=T)))

# Want to label/number each distinct group of unique (u,v) combinations
df %>% group_by(u,v) %>% mutate(label = n()) # WRONG: n() is number of element within its group, not overall number of group

   u v
1  2 3
2  1 3
3  1 2
4  2 3
5  1 2
6  3 3
7  1 3
8  1 2
9  3 1
10 3 4

KLUDGE 1: could do df %>% group_by(u,v) %>% summarize(label = n()) , then self-join

推荐答案

更新答案

get_group_number = function(){
    i = 0
    function(){
        i <<- i+1
        i
    }
}
group_number = get_group_number()
df %>% group_by(u,v) %>% mutate(label = group_number())

您还可以考虑以下稍微不可读的版本

You can also consider the following slightly unreadable version

group_number = (function(){i = 0; function() i <<- i+1 })()
df %>% group_by(u,v) %>% mutate(label = group_number())

---

使用 iterators package

library(iterators)

counter = icount()
df %>% group_by(u,v) %>% mutate(label = nextElem(counter))

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