按组排名变量（dplyr） [英] Rank variable by group (dplyr)
问题描述
我有一个数据列的列为 x1，x2，组，我想生成一个新的数据框，其列为 rank 表示 x1 在其组中的顺序。
I have a dataframe with columns x1, x2, group and I would like to generate a new dataframe with an extra column rank that indicates the order of x1 in its group.
有一个相关问题此处，但是接受的答案似乎不再起作用。
There is a related question here, but the accepted answer does not seem to work anymore.
直到此处，都可以：
library(dplyr)
data(iris)
by_species <- iris %>%
arrange(Species, Sepal.Length) %>%
group_by(Species)
但是当我尝试按组获取排名时：
But when I try to get the ranks by group:
by_species <- mutate(by_species, rank=row_number())
错误是：
等级错误（x，ties.method = first，na.last = keep）：
参数 x丢失，没有默认值
Error in rank(x, ties.method = "first", na.last = "keep") :
argument "x" is missing, with no default
更新
问题是 dplyr 和 plyr 。要重现该错误，请装入两个软件包：
The problem was some conflict between dplyr and plyr. To reproduce the error, load both packages:
library(dplyr)
library(plyr)
data(iris)
by_species <- iris %>%
arrange(Species, Sepal.Length) %>%
group_by(Species) %>%
mutate(rank=row_number())
# Error in rank(x, ties.method = "first", na.last = "keep") :
# argument "x" is missing, with no default
卸载 plyr 的工作原理如下：
detach("package:plyr", unload=TRUE)
by_species <- iris %>%
arrange(Species, Sepal.Length) %>%
group_by(Species) %>%
mutate(rank=row_number())
by_species %>% filter(rank <= 3)
## Sepal.Length Sepal.Width Petal.Length Petal.Width Species rank
## (dbl) (dbl) (dbl) (dbl) (fctr) (int)
## 1 4.3 3.0 1.1 0.1 setosa 1
## 2 4.4 2.9 1.4 0.2 setosa 2
## 3 4.4 3.0 1.3 0.2 setosa 3
## 4 4.9 2.4 3.3 1.0 versicolor 1
## 5 5.0 2.0 3.5 1.0 versicolor 2
## 6 5.0 2.3 3.3 1.0 versicolor 3
## 7 4.9 2.5 4.5 1.7 virginica 1
## 8 5.6 2.8 4.9 2.0 virginica 2
## 9 5.7 2.5 5.0 2.0 virginica 3
推荐答案
library(dplyr)
by_species <- iris %>% arrange(Species, Sepal.Length) %>%
group_by(Species) %>%
mutate(rank = rank(Sepal.Length, ties.method = "first"))
by_species %>% filter(rank <= 3)
##Source: local data frame [9 x 6]
##Groups: Species [3]
##
## Sepal.Length Sepal.Width Petal.Length Petal.Width Species rank
## (dbl) (dbl) (dbl) (dbl) (fctr) (int)
##1 4.3 3.0 1.1 0.1 setosa 1
##2 4.4 2.9 1.4 0.2 setosa 2
##3 4.4 3.0 1.3 0.2 setosa 3
##4 4.9 2.4 3.3 1.0 versicolor 1
##5 5.0 2.0 3.5 1.0 versicolor 2
##6 5.0 2.3 3.3 1.0 versicolor 3
##7 4.9 2.5 4.5 1.7 virginica 1
##8 5.6 2.8 4.9 2.0 virginica 2
##9 5.7 2.5 5.0 2.0 virginica 3
by_species %>% slice(1:3)
##Source: local data frame [9 x 6]
##Groups: Species [3]
##
## Sepal.Length Sepal.Width Petal.Length Petal.Width Species rank
## (dbl) (dbl) (dbl) (dbl) (fctr) (int)
##1 4.3 3.0 1.1 0.1 setosa 1
##2 4.4 2.9 1.4 0.2 setosa 2
##3 4.4 3.0 1.3 0.2 setosa 3
##4 4.9 2.4 3.3 1.0 versicolor 1
##5 5.0 2.0 3.5 1.0 versicolor 2
##6 5.0 2.3 3.3 1.0 versicolor 3
##7 4.9 2.5 4.5 1.7 virginica 1
##8 5.6 2.8 4.9 2.0 virginica 2
##9 5.7 2.5 5.0 2.0 virginica 3
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