R dplyr-以变量/汇总形式获取变量名作为字符串 [英] R dplyr - get variable name as string in mutate/summarise

问题描述

我一直在尝试提取传递给dplyr :: mutate（）中的函数的变量的名称，但未成功。下面是一个简短的示例，我想创建一个在mutate中返回字符串 mpg的函数：

I have been trying unsuccessfully to extract the name of a variable that was passed to a function in dplyr::mutate(). Below is a short example where I want to create a function that returns the string "mpg" inside mutate:

# mtcars dataset with grouping variable
dataset = mtcars
dataset$group = c(1, 2, 3, 4)

# function to call inside mutate()
f = function(col, data){
  str_col = deparse(lazyeval::expr_find(col))
  str_col
}

# this does not work: returns the content of mpg 
# instead of the variable name as a string
dataset %>%
  group_by(group) %>%
  mutate(f = f(mpg, dataset)
  ) %>%
  select(group, f)

我使用了lazyeval： ：expr_find（），因为据我所知文档仅可替代一层。当我在函数wrap（）中调用f（）时，它可以工作，但是当我将其放入group_by（）％>％mutate（）

I used lazyeval::expr_find(), because subsitute only "goes up" one layer as far as I understood the documentation. It works when I call f() inside the function wrap(), but it returns the content of mpg, instead of the name "mpg" when I put it inside group_by()%>%mutate()

我发现了一些相关的问题，但是没有一个问题可以解决我的问题。

I found some questions that are related, but none of them provided a solution to my problem.

任何帮助都非常感谢：)

Any help greatly appreciated:)

推荐答案

对于您要执行的操作，我还是不太清楚，但这也许会有所帮助：

I'm still not entirely clear on what you are trying to do, but maybe this helps:

f = function(col, data){
  str_col = deparse(substitute(col))
  data.frame(str_col)
}

dataset %>% 
   group_by(group) %>% 
   do(f(mpg, .))

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