Create a matrix of zeros and ones from R

Question

I want to create a matrix of 0s and 1s based on the following data.

    id <-c(1,1,1,2,2,3)
    x<- c(5,7,8,2,6,5)
    data_toy <- data.frame(id,x)
   data_toy%>% count(id) 

> data_toy%>% count(id) 
  id n
1  1 3
2  2 2
3  3 1

So based on the data, I need to create a 6X3 matrix where first column should be (1,1,1,0,0,0) and second column should be (0,0,0,1,1,0) so on.

Can you suggest anything to do this?

Thank you

Answer 1

We can use model.matrix in base R

model.matrix(~ factor(id) - 1, data_toy)

-output

#   factor(id)1 factor(id)2 factor(id)3
#1           1           0           0
#2           1           0           0
#3           1           0           0
#4           0           1           0
#5           0           1           0
#6           0           0           1

Or use table

with(data_toy, table(seq_along(id), id))