I would like to use the diag() function on a list of vectors, so as to get a list of matrices where the diagonals are the vectors of my list.
To be more specific, suppose I have a list called list of 100 vectors with 14 values each.
>dim(list)
100 14
I would like to create an array array of 100 matrices of size 14x14, where the diagonal of the matrix diag2vec(array[i,,]) is my vector list[i,] (all other values in the matrix to be 0).
So I would end up with:
>dim(array)
100 14 14
I tried using the diag() function, but I cannot get it to work row-wise.
(M <- matrix(1:6, nrow = 2))
# [,1] [,2] [,3]
# [1,] 1 3 5
# [2,] 2 4 6
sapply(1:nrow(M), function(i) diag(M[i, ]), simplify = "array")
# , , 1
#
# [,1] [,2] [,3]
# [1,] 1 0 0
# [2,] 0 3 0
# [3,] 0 0 5
#
# , , 2
#
# [,1] [,2] [,3]
# [1,] 2 0 0
# [2,] 0 4 0
# [3,] 0 0 6
Also, note that M is a matrix, not a list, and that dim applied to the last object returns 3 3 2, which is what you really want I think, instead of 2 3 3 as in your example.