Creating Identity Matrices in R

Question

I\'d like to create identity matrices of different sizes, and I\'m able to do so on a smaller scale like so:

> x <- matrix(cbind(c(1,0), c(0,1)), 2)
&g         


        

Answer 1

one (two) of the uses for diag when nrow is specified or when x is a vector of length one, you get an identity matrix

diag(5)
diag(nrow = 5)

or you could create a matrix of 0s and fill in the diagonal:

mat <- matrix(0, 5, 5)
diag(mat) <- 1

## or shorter:
`diag<-`(matrix(0, 5, 5), 1)

All of these give me:

#      [,1] [,2] [,3] [,4] [,5]
# [1,]    1    0    0    0    0
# [2,]    0    1    0    0    0
# [3,]    0    0    1    0    0
# [4,]    0    0    0    1    0
# [5,]    0    0    0    0    1