Dear List:

I am working to construct a matrix of a particular form. For the most
part, developing the matrix is simple and is built as follows:

vl.mat<-matrix(c(0,0,0,0,0,64,0,0,0,0,64,0,0,0,0,64),nc=4)

Now to expand this matrix to be block-diagonal, I do the following:

sample.size <- 100 # number of individual students
I<- diag(sample.size)
bd.mat<-kronecker(I,vl.mat)

This creates a block-diagonal matrix with variances along the diagonal
and covariances within-student to be zero (I am working with
longitudinal student achievement data). However, across student, I want
to have the correlation equal to 1 for each variance term. To
illustrate, here is a matrix for 2 students. The goal is for the
correlation between the second variance term for student 1 to be
perfectly correlated with the variance term for student 2. In other
words, I need to plug in 64 at position (6,2) and (2,6), another 64 at
position (7,3) and (3,7) and another 64 at positions (8,4) and (4,8).
I'm having some difficulty conceptualizing how to construct this part of
the matrix and would appreciate any thoughts.

Thank you,
Harold


     [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8]
[1,]    0    0    0    0    0    0    0    0
[2,]    0   64    0    0    0    0    0    0
[3,]    0    0   64    0    0    0    0    0
[4,]    0    0    0   64    0    0    0    0
[5,]    0    0    0    0    0    0    0    0
[6,]    0    0    0    0    0   64    0    0
[7,]    0    0    0    0    0    0   64    0
[8,]    0    0    0    0    0    0    0   64

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