taiwan-r-club-2022-10-06

(df <- data.frame(
  id = c(1,2,3),
  white = c(2,1,0),
  black = c(1,2,1)
  ))
#>   id white black
#> 1  1     2     1
#> 2  2     1     2
#> 3  3     0     1

id = c(rep(df$id, df$white), rep(df$id, df$black))
race = c(rep("white", sum(df$white)), rep("black", sum(df$black)))

df2 <- cbind(id, race)
(df2 <- df2[order(id),])
#>      id  race
#> [1,] "1" "white"
#> [2,] "1" "white"
#> [3,] "1" "black"
#> [4,] "2" "white"
#> [5,] "2" "black"
#> [6,] "2" "black"
#> [7,] "3" "black"