[jgrapht-developers] dumping adjacency and laplacian matrices

[Charles F. <cf...@us...>]

Hi,

Last week John invited me to join you, implementing myself some of the
long list of features that I recently requested. While I shall initially
be unable to implement at the same speed which I requested these
features, I do hope to make some contributions to JGraphT, which I have
already found to be enourmously useful, and which I anticipate using for
years to come.

John suggested that I announce my proposed changes on this mailing list
in an effort to solicit discussion on them prior to my implementation
efforts. I will thus start with the first piece of functionality which I
have already implemented externally, that I would like to add to
JGraphT.

Specifically, I would like to add the ability to dump graphs into
matrix representaitons which could in turn be analysed and manipulated
by external matrix software. You can read more about this idea in the
feature request number 1377955.

Sample output for the adjacency matrix would be:

1 2 1
1 3 1
2 1 1
3 1 1
3 4 1
4 3 1
5 5 0

Sample output for the Laplacian matrix would be:

1 1 2
1 2 -1
1 3 -1
2 2 1
2 1 -1
3 3 2
3 1 -1
3 4 -1
4 4 1
4 3 -1
5 5 0

The Laplacian could alternatively be in normalized form:

   http://mathworld.wolfram.com/LaplacianMatrix.html

John already suggested placing this in org._3pq.jgrapht.ext. Perhaps it
could be called MatrixExporter? Possible static method names would be
dumpAdjacencyMatrix and dumpLaplacianMatrix, but I'd love to hear other
ideas.

Any feedback on this proposed functionality is welcome.

thanks,
Charles

-- 
At intersections
Look each way
A harp sounds nice
But it's
Hard to play
Burma-Shave
http://burma-shave.org/jingles/1941/at_intersections