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A Function for Adding up Matrices with Different Dimensions

I couldnt find a function that can handle matrices with different dimensions and thus coded one myself.  It can sum up matrices and also copes with matrices with different dimensions.

# File: combmat.R
# Purpose: add up matrices with different dimensions
# Input: a list of 2-dimensional matrices
# Output: a combined matrix
# Author: Kay Cichini
# Date: Nov. 23th 2011
 
combmat <- function(m_l = list(NA)){
 n_m <- length(m_l) # no. of matrices used
 rownames_l <- lapply(m_l, rownames) # list of rownames
 colnames_l <- lapply(m_l, colnames) # list of colnames
 rownames_new <- unique(unlist(rownames_l)) # new, general rownames
 colnames_new <- unique(unlist(colnames_l)) # new, general colnames
 
 dimnames_new = list(rownames_new, colnames_new)
 m_new <- matrix(nrow = length(rownames_new),
 ncol = length(colnames_new),
 data = 0,
 dimnames = dimnames_new)
 
 m_interm_arr <- # array of intermediate 
 array(m_new, dim = c(length(rownames_new), # matrices with same no. of 
 length(colnames_new), n_m), # dimensions as elements in 
 dimnames = dimnames_new) # list of input matrices
 
 # take i-th element in list of imput matrices and add
 # its values according to the appropiate row and col indexes
 # in i-th dimension (i-th matrix) within array:
 for (i in 1:n_m) {
 m_interm_arr[,,i][rownames_l[[i]], colnames_l[[i]]] <- m_l[[i]]
 }
 return(apply(m_interm_arr, c(1,2), sum))
}
 
# Example:
print(m1 <- matrix(sample(1:40), 4, 10, dimnames = list(1:4,1:10)))
print(m2 <- matrix(sample(1:40), 10, 4, dimnames = list(1:10,1:4)))
 
combmat(m_l = list(m1, m2))

It is very likely that someone else may come to a more effective approach - Id be happy to here about improvements or if there is a package/function doing the same...

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