如何使用其他数据集变量作为其级别创建变量

Question

我有一个数据集，其中有两个变量被二分为“是”/“否”。

> df[1:20,]
# A tibble: 20 × 2
   black white
   <fct> <fct>
 1 No    Yes  
 2 No    Yes  
 3 No    Yes  
 4 No    Yes  
 5 No    Yes  
 6 No    Yes  
 7 No    Yes  
 8 No    Yes  
 9 No    Yes  
10 No    Yes  
11 No    Yes  
12 No    Yes  
13 No    Yes  
14 No    Yes  
15 No    Yes  
16 Yes   No   
17 No    Yes  
18 No    Yes  
19 No    Yes  
20 Yes   No 

这会创建很多变量(我的实际数据中有不止一个选项可供选择)，而且看起来不太整洁，因为它意味着许多不必要的变量。我想要创建一个新的变量(例如“种族”)，其中现在的单个变量“黑”、“白”等是该变量的级别。如本例所示

> df2[1:20,]
# A tibble: 20 × 1
   race 
   <fct>
 1 White
 2 White
 3 White
 4 White
 5 White
 6 White
 7 White
 8 White
 9 White
10 White
11 White
12 White
13 White
14 White
15 White
16 Black
17 White
18 White
19 White
20 Black

我该怎么做？

Answer 1

若要考虑多个种族，请在行(MARGIN = 1)上使用apply，并将列名粘贴到带有toString的"Yes"中。

df <- structure(list(asian = c("No", "No", "No", "No", "No", "No", "No", "No", "No", "No", "No", "No", "No", "No", "No", "No", "No", "No", "No", "Yes"), black = c("No", "No", "No", "No", "No", "No", "No", "No", "No", "No", "No", "No", "No", "No", "No", "Yes", "No", "No", "No", "Yes"), white = c("Yes", "Yes", "Yes", "Yes", "Yes", "Yes", "Yes", "Yes", "Yes", "Yes", "Yes", "Yes", "Yes", "Yes", "Yes", "No", "Yes", "Yes", "Yes", "No")), row.names = c(NA, -20L), class = c("tbl_df", "tbl", "data.frame"))

data.frame(race = apply(df == "Yes", 1, \(x) toString(colnames(df)[which(x)])))

           race
1         white
2         white
3         white
4         white
5         white
6         white
7         white
8         white
9         white
10        white
11        white
12        white
13        white
14        white
15        white
16        black
17        white
18        white
19        white
20 asian, black

使用max.col (只适用于每个人一个值)：

data.frame(race = colnames(df)[max.col(df == "Yes")])

Answer 2

使用dplyr (这假设在您的数据集中，一个人只能是一个种族)：

library(dplyr)

dat <- data.frame(id = 1:2,
                  black = c("No", "Yes"),
                  white = c("Yes", "No"))

dat |> mutate(
        race = case_when(black == "Yes" ~ "black",
                         white == "Yes" ~ "white")
)

输出：

#>   id black white  race
#> 1  1    No   Yes white
#> 2  2   Yes    No black