MATLAB: How to Draw a circle around a choosen node in a graph

3d plotsgraphplot

l have generated a topology of a network with 200 nodes.than l want to draw a circle with black color around a choosen node(satisfying a certain condition IF (condition) ). to simplify let the user introduce the the index of the node to circle with the black color. here is my code of the generated topology.l need to add wich instructions to draw the circle around the choosen node ?
    X=100; 
    Y=100;
    N=200; %number of nodes 
    nodesX(1)=rand*X;
    nodesY(1)=rand*Y;
    for i=2:N
        nodesX(i)=rand*X;
        nodesY(i)=rand*Y;
        d(i-1) =((nodesX(i)-nodesX(i-1)).^2+(nodesY(i)-nodesY(i-1)).^2).^0.5;
        while (d(i-1)>200)
           nodesX(i)=rand*X;
           nodesY(i)=rand*Y;
           d(i-1) =((nodesX(i)-nodesX(i-1)).^2+(nodesY(i)-nodesY(i-1)).^2).^0.5;
        end
    end
    h_old=plot(nodesX,nodesY,'m*');
    labels=[1:N]';
    labels=num2str(labels);
    text(nodesX,nodesY,labels);
    xlabel('X (Meters)');
    ylabel('Y (Meters)');
    title(['Network Topology with',num2str(N),'nodes']);
    hold on
    for k=1:N;
        for j=1:N;
            if (k~=j)
            d=((nodesX(k)-nodesX(j))^2+(nodesY(k)-nodesY(j))^2)^0.5;
            end
            if (k~=j);
                 if(d < 50);
                line([nodesX(k),nodesX(j)],[nodesY(k),nodesY(j)]);
                 end
            end
        end;
    end;

Best Answer

Hi,
I cannot understand fully your question or what do you want to generate. You could use a simple function to plot a circle on the given graph by giving circle center x,y and the radius r. e.g.
      function circle(x,y,r)
      %x and y are the coordinates of the center of the circle
      %r is the radius of the circle
      %0.01 is the angle step, bigger values will draw the circle faster but
      %you might notice imperfections (not very smooth)
      ang=0:0.01:2*pi; 
      xp=r*cos(ang);
      yp=r*sin(ang);
      plot(x+xp,y+yp,'k');
      end
or you could use a simple marker
       plot(nodesX(14),nodesY(14),'o','MarkerEdgeColor','k','MarkerSize',15)
       plot(nodesX(14),nodesY(14),'o','MarkerEdgeColor','k','MarkerSize',50)
node 14 is with marker and node 12 using circle function with r = 1 meter i.e.
       circle(nodesX(12),nodesY(12),1)
Regards,
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