R creating an array of matrices

Question

I would like to create an array of matrices in such a way that I first create an array of k matrices with NA values and then loop over k and update each k'th matrix through the array.

Any suggestions?

Answer 1

I'm probably missing the point, but won't:

k = 2; n=3; m = 4
array(NA, c(n,m,k))

, , 1

     [,1] [,2] [,3] [,4]
[1,]   NA   NA   NA   NA
[2,]   NA   NA   NA   NA
[3,]   NA   NA   NA   NA

, , 2

     [,1] [,2] [,3] [,4]
[1,]   NA   NA   NA   NA
[2,]   NA   NA   NA   NA
[3,]   NA   NA   NA   NA

give you what you want? Then you can loop as normal:

R> for(k in 1:2){print(a[,,k])}

Answer 2

Beware of terminology :-) . As CSGillespie points out, you can define an N-rank array in R . Alternatively, you could create a list variable, each entry of which contains a matrix. The advantage to the latter is that the matrices can be of differing sizes. The disadvantage is that it can be rather more painful to create the inital state.

E.g.

mat1 <- matrix(NA, 3,5)
mat2 <- matrix(NA, 4,7)
matlist <- list(mat1=mat1,mat2=mat2)