One hot encode list of vectors

Question

Is there a quick way to one-hot encode lists of vectors (with different lenghts) in R, preferably using tidyverse?

For example:

vals <- list(a=c(1), b=c(2,3), c=c(1,2))

The wanted result is a wide dataframe:

   1   2   3
a  1   0   0
b  0   1   1
c  1   1   0

Thanks!

Answer 1

We can enframe the list and convert them into separate rows, create a dummy column and convert the data into wide-format using pivot_wider.

library(tidyverse)

enframe(vals) %>%
  unnest(value) %>%
  mutate(temp = 1) %>%
  pivot_wider(names_from = value, values_from = temp, values_fill = list(temp = 0))

#  name    `1`   `2`   `3`
#  <chr> <dbl> <dbl> <dbl>
#1 a         1     0     0
#2 b         0     1     1
#3 c         1     1     0

Answer 2

One base R option could be:

t(table(stack(vals)))

   values
ind 1 2 3
  a 1 0 0
  b 0 1 1
  c 1 1 0