是否可以根据变量标签选择列？

对于非常广泛的数据集，是否可以使用变量标签来选择列？

library(expss)
data(mtcars)
mtcars = apply_labels(mtcars,
                      mpg = "Miles/(US) gallon",
                      cyl = "Number of cylinders",
                      disp = "Displacement (cu.in.)",
                      hp = "Gross horsepower",
                      drat = "Rear axle ratio",
                      wt = "Weight (1000 lbs)",
                      qsec = "1/4 mile time",
                      vs = "Engine",
                      vs = c("V-engine" = 0,
                             "Straight engine" = 1),
                      am = "Transmission",
                      am = c("Automatic" = 0,
                             "Manual"=1),
                      gear = "Number of forward gears",
                      carb = "Number of carburetors"
)
mtcars %>% 
  select(contains("Miles"))

这不起作用，因为它会查找列名称。它可以查看标签吗？

编辑：我应该添加，除了将标签转换为列名称的明显作用之外。

我们可以得到attributes“标签”，检查“里程”

library(dplyr)
library(stringr)
mtcars %>% 
   select(where(~ str_detect(attributes(.)$label, 'Miles')))

-output

#                      mpg
#Mazda RX4           21.0
#Mazda RX4 Wag       21.0
#Datsun 710          22.8
#Hornet 4 Drive      21.4
#Hornet Sportabout   18.7
#Valiant             18.1
#Duster 360          14.3
#Merc 240D           24.4
#Merc 230            22.8
#Merc 280            19.2
#Merc 280C           17.8
#Merc 450SE          16.4
# ..

或者使用base R (with R 4.1.0)，用循环遍历列lapply，提取labels属性、用途grep返回匹配的元素pattern“英里”，获取names并将其用于select of subset

mtcars |>  
    lapply(\(x) attributes(x)$label) |> 
    grep(pattern = 'Miles', value = TRUE) |> 
    names() |>
    {\(x) subset(mtcars, select = x)}()

-output

#                      mpg
#Mazda RX4           21.0
#Mazda RX4 Wag       21.0
#Datsun 710          22.8
#Hornet 4 Drive      21.4
#Hornet Sportabout   18.7
#Valiant             18.1
#Duster 360          14.3
#Merc 240D           24.4
#Merc 230            22.8
#Merc 280            19.2
# ...