Question

我过去常常使用group_by_

library(dplyr)
group_by <- c('cyl', 'vs')
mtcars %>% group_by_(.dots = group_by) %>% summarise(gear = mean(gear))

但现在不推荐使用group_by_。我不知道如何使用tidy evaluation framework。

Answer 1

将字符向量转换为符号列表并将其拼接在

中

df %>% group_by(!!! syms(group_by))

Answer 2

group_by_at有group_by个变体：

library(dplyr)
group_by <- c('cyl', 'vs')
mtcars %>% group_by_at(group_by) %>% summarise(gear = mean(gear))

上面是广义的简化版本：

mtcars %>% group_by_at(vars(one_of(group_by))) %>% summarise(gear = mean(gear))

在vars内，您可以使用任何dplyr方式来选择变量：

mtcars %>%
    group_by_at(vars(
        one_of(group_by) # columns from predefined set
        ,starts_with("a") # add ones started with a
        ,-hp # but omit that one
        ,vs # this should be always include
        ,contains("_gr_") # and ones with string _gr_
    )) %>%
    summarise(gear = mean(gear))

group_by使用整齐的评估语义的字符向量

2 个答案: