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how create coordinate array?

Asked by huda nawaf on 8 Sep 2012

hi,

I found this function to plot the graph of adjacency matrix.

http://stackoverflow.com/questions/5721377/plotting-a-graph-from-its-adjacency-matrix

The input is adj matrix and coordinates array, xy. I have adj matrix , but I do not know how create coordinate array.

please can anybody help me in this regarding?

thanks

1 Comment

Oleg Komarov on 8 Sep 2012

Which is already part of MATLAB: gplot().

huda nawaf

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2 Answers

Answer by nanren888 on 8 Sep 2012

huda nawaf,

Interesting that the Mathworks copyright is still in the code you are using. It is not clear what is added to gplot by the addition.

gplot has an example in doc: try doc gplot

It seems as a graph has no inherent shape, that you must provide the xy points for each node for it. The example in doc shows a Buckyball node layout.

I've never used gplot before. I read the help, read doc gplot, played a few minutes & have this.

 x = 1:2;
 y = 1:3;
 [XX,YY] = meshgrid(x,y);
 a = (rand([2*3,2*3])>0.8);
 P=[XX(:),YY(:)];
 gplot(a,P,'-*');
 axis([0,7,0,7]);
 a
 P

a =

     0     0     0     0     0     1
     0     0     1     1     0     1
     0     0     1     1     0     0
     0     0     0     0     0     0
     0     0     1     0     0     1
     0     0     1     0     1     1

P =

     1     1
     1     2
     1     3
     2     1
     2     2
     2     3

Maybe it will help a little?

4 Comments

Walter Roberson on 8 Sep 2012

Your earlier questions indicated that any outlay was acceptable. Are you now imposing restrictions about lines not overlapping, lines not crossing, or something like that?

huda nawaf on 9 Sep 2012

no walter, my erlier question is see the cluster visually. Now, I need see the nodes of adjacancy matrix how connect to each other.

that figure is not relate with the above matrix.

please, inform me how I can send image , then others see it. I think I sent image in previous time but nobody saw it.

thanks

nanren888
Answer by Walter Roberson on 9 Sep 2012

If all you have is the adjacency matrix, then even if the weights of the vertices can be interpreted as distances, it is difficult to reconstruct a planar graph. Oh, algebraically it can be done, but it involves solving (N^2)/2 simultaneous non-linear equations, and that gets very time consuming extremely quickly.

So, you might as well just use rand() to generate random x and y coordinates and graph using those.

4 Comments

Walter Roberson on 10 Sep 2012

random coordinates can do that.

huda nawaf on 13 Sep 2012

thanks walter, please show me how do that with random coordinates

Walter Roberson on 13 Sep 2012
xy = rand(NumberOfNodes, 2);

I suspect that likely NumberOfNodes = size(AdjacencyMatrix, 1);

Walter Roberson

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