# What is the name of the matrices which reorder edges in an adjancency so that they are closer to the diagonal? (modularity/structure)

I have seen adjacency matrices presented where the edges formed box like formations along the diagonal (not block matrices). This helped view the modularity and community structure of the group of edges/connectivity. It appears as if they optimize a cost funtion to minimize the distance from the diagonal

What is the name of those types of matrices? How are they formed from an original adjacency matrix? What algorithms or methods perform this type of reordering to view this modularity?

Are 'bridge connections' visible from them?

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Figure3 and upper left plot is an example - people.maths.ox.ac.uk/porterm/papers/… –  Vass Jan 24 '13 at 17:54
are they band matrices? en.wikipedia.org/wiki/Band_matrix –  Vass Jan 24 '13 at 19:27