Goal:
Suppose you have a vector that is a discrete variable with values ranging
from 1 to 3, and length of 10.  We'll use this as the example:

y <- c(1,2,3,1,2,3,1,2,3,1)

...and suppose you want your new vector (y.new) to be equal in length to the
possible discrete values (3) times the length (10), and formatted in such a
way that if y[1] == 1, then y.new[1:3] == c(1,0,0), and if y[2] == 2, then
y.new[4:6] == c(0,1,0).  For example, the final goal should be:

y.new <- c(1,0,0,0,1,0,0,0,1,1,0,0,0,1,0,0,0,1,1,0,0,0,1,0,0,0,1,1,0,0)

Note: I know how to do this with loops, but that's not taking advantage of
R's capabilities with vectors and, I suspect, matrices.

So far, my best guess would be to start as follows:

y1 <- ifelse(y == 1, 1, 0)
y2 <- ifelse(y == 2, 1, 0)
y3 <- ifelse(y == 3, 1, 0)

>From here, maybe put these into a 10x3 matrix, and read them out by row into
y.new?  Is that even the most efficient way?  If it is, I'm sure I can get
them into a matrix, but how do I read them out correctly?  Thanks for any
input.
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