变异管道中的case_when

Question

在dplyr::mutate调用中，dplyr::case_when似乎不像其他命令那样工作。例如：

library(dplyr)

case_when(mtcars$carb <= 2 ~ "low",
          mtcars$carb > 2 ~ "high") %>% 
  table

作品：

.
high  low 
  15   17 

但是把case_when放在mutate链中：

mtcars %>% 
  mutate(cg = case_when(carb <= 2 ~ "low",
                        carb > 2 ~ "high"))

然后你会得到：

 Error: object 'carb' not found

虽然这样做没什么问题

mtcars %>% 
  mutate(cg = carb %>% 
           cut(c(0, 2, 8)))

Answer 1

从dplyr的0.7.0版本开始，case_when在mutate中的工作方式如下：

library(dplyr) # >= 0.7.0
mtcars %>% 
  mutate(cg = case_when(carb <= 2 ~ "low",
                        carb > 2  ~ "high"))

欲了解更多信息，请访问：http://dplyr.tidyverse.org/reference/case_when.html

Answer 2

我们可以使用.$

mtcars %>%  
     mutate(cg = case_when(.$carb <= 2 ~ "low",  .$carb > 2 ~ "high")) %>%
    .$cg %>%
    table()
# high  low 
#  15   17 

Answer 3

library(dplyr) #loading the dplyr package

content150_fortified <- content150 %>% #creating a new variable
mutate(number_yn = case_when( #creating a new column using mutate
        number >= 18 & number <=25 ~ "no", # if number is "none", make number_yn "no"
        number!="none" ~ "yes"  # if number is not "none", make number_yn "yes"
        )
      )