generate_undirected_graph.m

function [undirectedGraph,unedges]=generate_undirected_graph(map,nodelocation)
% takes map and produce undirected map and its adge set

% take number of node
nnode=size(nodelocation,1);
% set graph and edges as zero
undirectedGraph=zeros(nnode,nnode);
unedges=[];

%generate undirected graph

for i=1:nnode-1 
    for j=i+1:nnode
        % take each pair of node^s location x and y
        x1=[nodelocation(i,1);nodelocation(j,1)];
        y1=[nodelocation(i,2);nodelocation(j,2)];  
        % check this two nodes intersect any obstacle or not
        [xi,yi] = polyxpoly(x1,y1,map.obsx,map.obsy);
        % if there is not any intersection
        if length(xi)==0
            % connect this two nodes in graph
            undirectedGraph(i,j)=1;
            undirectedGraph(j,i)=1;
            % add this connection to adge set
            unedges=[unedges;i j;j i];
        end
    end
end
% plot graph
hold on;
for i=1:2:size(unedges,1)
    x1=[nodelocation(unedges(i,1),1);nodelocation(unedges(i,2),1)];
    y1=[nodelocation(unedges(i,1),2);nodelocation(unedges(i,2),2)]; 
    line(x1,y1);
end
hold off;