R按组进行分位数分配 [英] R quantile by groups with assignments

问题描述

我有以下df:

group = rep(seq(1,3),30)
variable = runif(90, 5.0, 7.5)
df = data.frame(group,variable)

我需要i)按组定义分位数，ii)根据每个人的组将每个人分配给她的分位数.

I need to i) Define quantile by groups, ii) Assign each person to her quantile with respect to her group.

因此，输出将如下所示:

Thus, the output would look like:

id    group  variable  quantile_with_respect_to_the_group
1      1      6.430002     1
2      2      6.198008     3
          .......

有一种复杂的方法可以在每个组上使用循环和剪切功能，但这根本没有效率.有人知道更好的解决方案吗?

There is a complicated way to do it with loops and cut function over each groups but it is not efficient at all. Does someone know a better solution ?

谢谢！

推荐答案

在data.table中:

library(data.table)

setDT(df)[,quantile := cut(variable, quantile(variable, probs = 0:4/4),
                         labels = FALSE, include.lowest = TRUE), by = group]

>head(df)
#    group variable quantile
# 1:     1 6.103909        2
# 2:     2 6.511485        3
# 3:     3 5.091684        1
# 4:     1 6.966461        4
# 5:     2 6.613441        4

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