How to get rid of duplicate rows preserving information into another column in R?

I am trying to get rid of duplicates from a dataset and I just found out that the rows are not exactly the same. Thus, I am trying to preserve the information and generate another column. For example, suppose I have the following data:

df <- data.frame(id = c("a", "a", "b", "c", "c", "d"),
                color = c("red", "blue", "green", "blue", "green","red"))

> df
  id color
1  a   red
2  a  blue
3  b green
4  c  blue
5  c green
6  d   red

Now, I would like to have no repetitive ids, thus I would like the extra information to be on another column. The result should be something like this:

> df2
  id color color2
1  a   red   blue
2  b green       
3  c  blue  green
4  d   red

Is there a simple way to accomplish this?

Solution

Here's one way to do this with tidyverse packages

library(dplyr)
library(tidyr)

df %>%
  mutate(n = row_number(),
         .by = id) %>%
  pivot_wider(
    names_from = n,
    names_prefix = 'color_',
    values_from = color
  )
#> # A tibble: 4 × 3
#>   id    color_1 color_2
#>   <chr> <chr>   <chr>  
#> 1 a     red     blue   
#> 2 b     green   <NA>   
#> 3 c     blue    green  
#> 4 d     red     <NA>

^{Created on 2023-10-18 with reprex v2.0.2}