42 lines
1.3 KiB
Matlab
42 lines
1.3 KiB
Matlab
% Finds the dual of a graph; a dual is the inverted nodes-edges graph
|
|
% This is also called the line graph, adjoint graph or the edges adjacency
|
|
%
|
|
% INPUTs: adjacency (neighbor) list representation of the graph (see adj2adjL.m)
|
|
% OUTPUTs: adj (neighbor) list of the corresponding dual graph and
|
|
% cell array of [original] edges, i.e. the new nodes
|
|
%
|
|
% Note: This routine only works for undirected, simple graphs.
|
|
% GB: last updated, Sep 23 2012
|
|
|
|
function [dL,edge_array] = graphDual(L)
|
|
|
|
dL={}; % initialize
|
|
for i=1:length(L)
|
|
for j=1:length(L{i})
|
|
|
|
if i<=L{i}(j); dL{length(dL)+1}=[]; end
|
|
|
|
end
|
|
end
|
|
|
|
edge_array={};
|
|
|
|
for i=1:length(L)
|
|
|
|
for j=1:length(L{i}) % add i,L{i}j to list of nodes
|
|
if i<=L{i}(j); edge_array{length(edge_array)+1}= strcat(num2str(i),'-',num2str(L{i}(j))); end
|
|
end
|
|
|
|
for j=1:length(L{i}) % add i - L{i}j to list of edges
|
|
for k=j+1:length(L{i})
|
|
edge1=strcat(num2str(min([i,L{i}(j)])),'-',num2str(max([i,L{i}(j)])));
|
|
edge2=strcat(num2str(min([i,L{i}(k)])),'-',num2str(max([i,L{i}(k)])));
|
|
|
|
ind_edge1=find(ismember(edge_array, edge1)==1);
|
|
ind_edge2=find(ismember(edge_array, edge2)==1);
|
|
|
|
dL{ind_edge1}=unique([dL{ind_edge1},ind_edge2]);
|
|
dL{ind_edge2}=unique([dL{ind_edge2},ind_edge1]);
|
|
end
|
|
end
|
|
end |