如何使用mutate()创建一个变量，该变量的值等于给定变量的标签? [英] How do I create a variable with mutate() that has values equal to the label of a given variable?

问题描述

我正在尝试在我已使用 gather()的 data.frame 上使用 mutate()来创建一个变量，该变量的值是所收集的变量的 label().我已经搜索了Google和StackOverflow，但没有找到合适的答案.我的研究使我认为可能需要标准评估.

I am trying to use mutate() on a data.frame that I have used gather() on to create a variable whose values are the label() for the gathered variable. I have searched Google and StackOverflow and have not found a suitable answer. My research led me to think that standard evaluation might be needed.

这是一个最小的可重现示例:

Here is a minimal reproducible example:

# Packages
library(dplyr)
library(Hmisc)
library(tidyr)
library(lazyeval)

df <- mtcars %>% 
tbl_df() %>%
slice(1)

label(df$mpg) <- "Miles per gallon"
label(df$cyl) <- "Cylinders"

df %>% 
select(mpg, cyl) %>%
gather(variable, value) %>% 
mutate_(.dots = interp(~attr(df$x, "label"), x = variable))

此代码产生:

# A tibble: 2 × 3
  variable value `attr(df$mpg, "label")`
     <chr> <dbl>                   <chr>
1      mpg    21        Miles per gallon
2      cyl     6        Miles per gallon

这显然只是获得 mpg 的标签.

which is clearly only getting the label for mpg.

我的目标是拥有类似的东西

My goal is to have something like:

# A tibble: 2 × 3
      variable value `attr(df$variable, "label")`
         <chr> <dbl>                   <chr>
    1      mpg    21        Miles per gallon
    2      cyl     6        Cylinders

推荐答案

这是什么?

df %>% 
    select(mpg, cyl) %>%
    gather(variable, value) %>% 
    mutate(labels = label(df)[variable])

# A tibble: 2 × 3
  variable value           labels
     <chr> <dbl>            <chr>
1      mpg    21 Miles per gallon
2      cyl     6        Cylinders

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