[R] Kronecker matrix product

[Robin Hankin]

Hi

I want to write a little function that takes a matrix X of size
m-by-n, and a list L of length  "m",  whose elements are matrices all  
of which have
the same number of columns but possibly a different number of rows.

I then want to get a sort of dumbed-down kronecker product in which
X[i,j] is replaced by X[i,j]*L[[j]]

where L[[j]] is the j-th of the "m" matrices.  For example, if

X = matrix(c(1,5,0,2),2,2)

and

L[[1]] = matrix(1:4,2,2)
L[[2]] = matrix(c(1,1,1,1,1,10),ncol=2)

I want


      [,1] [,2] [,3] [,4]
[1,]    1    3    0    0
[2,]    2    4    0    0
[3,]    5    5    2    2
[4,]    5    5    2    2
[5,]    5   50    2   20
 >


see how, for example, out[3:5,1:2]  == 5*L[[2]], the "5" coming from X 
[2,1].

[
I can bind L together into a single matrix with

do.call("rbind",L)

and calculate the number of rows with

sapply(L,nrow)

but I don't see how this can help.
]






--
Robin Hankin
Uncertainty Analyst
National Oceanography Centre, Southampton
European Way, Southampton SO14 3ZH, UK
  tel  023-8059-7743