如何在group_by中传递变量名 [英] How to pass a variable name in group_by
问题描述
我可以使用以下代码计算组name1中数据框df中值(val)的排名:
I can calculate the rank of the values (val) in my dataframe df within the group name1 with the code:
res <- df %>% arrange(val) %>% group_by(name1) %>% mutate(RANK=row_number())
我不想在代码中写入 name1列,而是希望将其作为变量传递,例如crit = name1。但是,下面的代码不起作用,因为假定crit1是列名而不是变量名。
Instead of writing the column "name1" in the code, I want to pass it as variable, eg crit = "name1". However, the code below does not work since crit1 is assumed to be the column name instead of a variable name.
res <- df %>% arrange(val) %>% group_by(crit1) %>% mutate(RANK=row_number())
如何在代码中传递crit1?
How can I pass crit1 in the code?
谢谢,
Tom
Thanks, Tom
推荐答案
我们可以使用 group_by _
library(dplyr)
df %>%
arrange(val) %>%
group_by_(.dots=crit1) %>%
mutate(RANK=row_number())
#Source: local data frame [10 x 4]
#Groups: name1, name2 [7]
# val name1 name2 RANK
# <dbl> <chr> <chr> <int>
#1 -0.848370044 b c 1
#2 -0.583627199 a a 1
#3 -0.545880758 a a 2
#4 -0.466495124 b b 1
#5 0.002311942 a c 1
#6 0.266021979 c a 1
#7 0.419623149 c b 1
#8 0.444585270 a c 2
#9 0.536585304 b a 1
1#0 0.847460017 a c 3
更新
group_by _
在最新版本中已弃用(现在使用 dplyr
版本- 0.8.1
),因此我们可以使用 group_by_at
将字符串向量作为输入变量
Update
group_by_
is deprecated in the recent versions (now using dplyr
version - 0.8.1
), so we can use group_by_at
which takes a vector of strings as input variables
df %>%
arrange(val) %>%
group_by_at(crit1) %>%
mutate(RANK=row_number())
或者另一种选择是转换为符号( syms
来自 rlang
)并评估( !!!
)
df %>%
arrange(val) %>%
group_by(!!! rlang::syms(crit1)) %>%
mutate(RANK = row_number())
data
data
set.seed(24)
df <- data.frame(val = rnorm(10), name1= sample(letters[1:3], 10, replace=TRUE),
name2 = sample(letters[1:3], 10, replace=TRUE),
stringsAsFactors=FALSE)
crit1 <- c("name1", "name2")
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