r - 创建一个虚拟变量列来指示记录是否位于第二个数据帧中？

Question

我有两个数据帧，df1 和 df2，采用这样的格式(最后用于数据输入的可重现代码):

df1
#>             name instrument
#> 1    John Lennon     guitar
#> 2    Mick Jagger     vocals
#> 3    Ringo Starr      drums
#> 4 Keith Richards     guitar

和

df2
#>              name beatles
#> 1     John Lennon       1
#> 2     Ringo Starr       1
#> 3 George Harrison       1
#> 4  Paul McCartney       1

我想向 df1 添加一列，指示记录是否也在 df2 中(如果没有则等于 0)，所以我想要的输出是:

output
#>             name instrument beatles
#> 1    John Lennon     guitar       1
#> 2    Mick Jagger     vocals       0
#> 3    Ringo Starr      drums       1
#> 4 Keith Richards     guitar       0

我已经尝试过 full_join()，但这会跨过 df2 中不在 df1 中的行，这不是我想要的。 (即 George Harrison 和 Paul McCartney 行不应出现在输出中)

library(tidyverse)

df1 %>% 
  full_join(df2) 

#> Joining, by = "name"
#>              name instrument beatles
#> 1     John Lennon     guitar       1
#> 2     Mick Jagger     vocals      NA
#> 3     Ringo Starr      drums       1
#> 4  Keith Richards     guitar      NA
#> 5 George Harrison       <NA>       1
#> 6  Paul McCartney       <NA>       1

可重现的代码如下:

df1 <- data.frame(stringsAsFactors=FALSE,
         name = c("John Lennon", "Mick Jagger", "Ringo Starr", "Keith Richards"),
   instrument = c("guitar", "vocals", "drums", "guitar")
)

df2 <- data.frame(stringsAsFactors=FALSE,
                name = c("John Lennon", "Ringo Starr", "George Harrison",
                         "Paul McCartney"),
          beatles = c(1, 1, 1, 1)
       )

library(tidyverse)

df1 %>% 
  full_join(df2) 

Answer 1

df1$beatles <- ifelse(df1$name %in% df2$name, 1, 0)

            name instrument beatles
1    John Lennon     guitar       1
2    Mick Jagger     vocals       0
3    Ringo Starr      drums       1
4 Keith Richards     guitar       0

或者，如果 df2 中还有其他乐队，您可以这样做:

df1$beatles <- ifelse(df1$name %in% df2[df2$beatles == 1,]$name, 1, 0)