MATLAB: How to find if graph is connected

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I'm trying to create Geometric random graph and here is my code I wrote that is not done yet.
    % code
n = input('Enter number of nodes: ');
x=[];
y=[];
d=[];
x = rand(1,n);
y = rand(1,n);
for i = 1 : (n)
    for j = 1 : (n)
      d(i, j) = sqrt((x(i) - x(j)) ^ 2 + (y(i) - y(j)) ^ 2); 
           //finding distance of each nodes
    end
end
R=0.3; //radius
   edge = d <= R ;
I'm trying to find if the nodes are connected or not but I don't have any idea what I can use to find the answer. Please help.

Best Answer

I think this is what you are looking for. The line with the variable 'con' is not really necessary, but if you need to reference the connections later it would be convenient.
R=0.3; %%radius
n = input('Enter number of nodes: ');
d=zeros(n,n);
con=zeros(n,n); % matrix of zeros indicates none are connected
x = rand(1,n);
y = rand(1,n);
plot(x,y,'o');
hold on
for i = 1 : (n)
    for j = 1 : (n)
      d(i, j) = sqrt((x(i) - x(j)) ^ 2 + (y(i) - y(j)) ^ 2); 
           if (d(i,j)<R)
               con(i,j)=1; % sets to 1 to indicate connection between node i and j
               hold on
               line([x(i), x(j)],[y(i), y(j)]);
           end
    end
end
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