R: create dummy variables based on a categorical variable *of lists* [duplicate]

Answer 1

We can use mtabulate

library(qdapTools)
cbind(df[1], mtabulate(df$y))
#  x A B C D E
#1 1 1 0 0 0 0
#2 2 1 1 0 0 0
#3 3 0 0 1 0 0
#4 4 0 1 1 1 0
#5 5 0 0 0 0 1