convert dataframe to binary features in r

Question

I have a dataframe:

participants <- c(A, A, A, B, C, C)

answers <- c(alpha, beta, gamma, beta, beta, gamma)

participants answers
A            alpha
A            beta
A            gamma
B            beta
C            beta
C            gamma

The 'answers' column contains many more than just this little set.

how do I make it into binary features like the following:

participant answers value
A           alpha   1
A           beta    1
A           gamma   1
B           alpha   0
B           beta    1
B           gamma   0
C           alpha   0
C           beta    1
C           gamma   1

My guess is that I have to get the levels of the 'answers' and the 'participants' too?

But I'm not sure how to do it next. Thanks!

Answer 1

In base R you could do:

data.frame(table(df1))
  participants answers Freq
1            A   alpha    1
2            B   alpha    0
3            C   alpha    0
4            A    beta    1
5            B    beta    1
6            C    beta    1
7            A   gamma    1
8            B   gamma    0
9            C   gamma    1

The above is not ordered the same way as your table. To do that, you could do:

with(a<-data.frame(table(df1)), a[order(participants),])
  participants answers Freq
1            A   alpha    1
4            A    beta    1
7            A   gamma    1
2            B   alpha    0
5            B    beta    1
8            B   gamma    0
3            C   alpha    0
6            C    beta    1
9            C   gamma    1