R or MATLAB: permute a large sparse matrix into a block diagonal matrix

Question

I have a large sparse matrix, and I want to permute its rows or columns to turn the original matrix into a block diagonal matrix. Anyone knows which functions in R or MATLAB can do this? Thanks a lot.

Answer 1

I'm not really set up to test this, but for a matrix m I would try:

p = symrcm(m);
block_m = m(p,p);

If that doesn't work, look through the other functions listed in help sparfun to see if any will help you out.

Answer 2

该seriation包R具有在与此相关的一个问题的一些工具。

Answer 3

Not exactly sure if this is what you want, but in MATLAB this is what I have used in the past. Probably not the most elegant solution. I go from sparse to full and then chop the thing into square blocks.

A=full(A);

Then:

blockedmatrix = mat2cell(A, (n*ones(1,size(A,1)/n)), ...
(n*ones(1,size(A,1)/n))); %found somewhere on internetz

This returns a cell, where each entry is of size nxn. It's easy to extract the blocks of interest, manipulate them, and then restore them to a matrix with cell2mat.

Answer 4

Maybe a bit late to the game, but since there are available commands, here is a simple one. If you have a matrix H and the block diagonal form is needed, you can obtain it through the following lines ( MATLAB ):

[p,q] = dmperm(H);
H(p,q)

which is equivalent to Dulmage - Mendelsohn permutation.