Fixed node locations using graphplot() with Markov chains

Hi,

I have developed a few lines of code to generate markov chains from a transition vector ('stagesVec'). The code works well and I now wish to compare multiple transition vectors. If I run the code a second time with a second transition vector I get a new Markov chain with the new infromation.

My problem is this, the two Markov chains have the same nodes, however the nodes move (plotting location) between graphs, this makes a visual inspection very difficult. I would like for the nodes to remain in the same place, but edges (the connecting lines between the nodes) to be removed as required by the probability matrix. I will include a couple of images below to hopefully make this easier to understand! I have had a look at both doc graphplot and figure -> edit but cannot see anything obvious.

Thanks for the help,

Christopher

tm = full(sparse(stagesVec(1:end-1),stagesVec(2:end),1));
stateNames = ["N1" "N2" "N3" "R" "U" "W" ];
mc = dtmc(tm,"StateNames",stateNames);
figure()
graphplot(mc);

Answer 1

[Steven Lord]

Store the handle of the GraphPlot in a variable, h1 in the code below.

adjacency1 = sprand(6, 6, 0.2);
D1 = digraph(adjacency1);
h1 = plot(D1);

When you plot the second graph or digraph, specify the XData and YData name-value pair arguments using the XData and YData properties of the GraphPlot created from the first graph or digraph.

adjacency2 = sprand(6, 6, 0.2);
D2 = digraph(adjacency2); % Different digraph
h2 = plot(D2, 'XData', h1.XData, 'YData', h1.YData);

To show that the second digraph, if left to its own devices, would plot the nodes in different locations:

h3 = plot(D2);

[Christopher McCausland]

Hi Steven,

Sorry for the slow reply on this, its been a busy few days!

I wanted to say thank you for a great indepth answer, I hadn't realised that the graphplot X and Y handles were specified as such, this is really handy to know!

I have tried to implement this;

nodePlace = graphplot(mc); % Created the first graph and store it in nodePlace
graphplot(mc,'XData', nodePlace.XData, 'YData', nodePlace.YData); % Use the .XData and .YData stored handles 

The problem being that graphplot() doesn't accept 'XData', 'YData' as an input. I suspect this is why you swapped to just plot(), hopwever plot() doesn't accept a 1x1 dtmc object (markov chain 'mc') being passed to it. Am I missing soemthing obvious?

Christopher

[Christopher McCausland]

Hi Steven,

Never mind I have discovered my error, you (very cleverly) use the digraph() command inside the plot() command, for anyone else, it should look like this:

nodePlace = graphplot(mc);
D2 = digraph(mc.P,mc.StateNames); % Different digraph
h2 = plot(D2, 'XData', nodePlace.XData, 'YData', nodePlace.YData);

I will probably generate two vectors at the start for the X and Y data but this now makes much more sense in terms of the the calls are handled. Thank you so much for your help!

Christopher