One-hot-encoding a R list of characters

Question

I have the following R dataframe :

id    color
001   blue
001   yellow
001   red
002   blue
003   blue
003   yellow

What's the general method to one-hot-encode such a dataframe into the following :

id    blue    yellow    red
001   1       1         1
002   1       0         0
003   1       0         1

Thank you very much.

Answer 1

Try this. You can create a variable for those observations present in data equals to one and then use pivot_wider() to reshape the values. As you will get NA for classes not present in data, you can replace it with zero using replace(). Here the code using tidyverse functions:

library(dplyr)
library(tidyr)
#Code
dfnew <- df %>% mutate(val=1) %>%
  pivot_wider(names_from = color,values_from=val) %>%
  replace(is.na(.),0)

Output:

# A tibble: 3 x 4
     id  blue yellow   red
  <int> <dbl>  <dbl> <dbl>
1     1     1      1     1
2     2     1      0     0
3     3     1      1     0

Some data used:

#Data
df <- structure(list(id = c(1L, 1L, 1L, 2L, 3L, 3L), color = c("blue", 
"yellow", "red", "blue", "blue", "yellow")), class = "data.frame", row.names = c(NA,-6L))