How to define visibility graph criterion in matlab code

Dear colleagues,

   Could you give me assistances? How to define visibility graph criterion in matlab code? Many thanks!

Answer 1

[Bruce Priddy]

There is a Fortran code for the Horizontal Visibility Graph at

http://www.maths.qmul.ac.uk/~lacasa/Software.html

and the code below for regular visibilty graph which I have not tried but looks incomplete

function varargout=visgraph(varargin)
[k,logP]=visgraph(x)
%Generate Conway Series
 N=1000;
 a=ones(N,1);
 out=ones(N,1);
 for n=3:N
     a(n)=a(a(n-1))+ a(n-a(n-1));
     out(n)= a(n) - (n/2);
end
 %Generate Surrogate Data
 nS=5;
 S=surrogate(out,nS);
 subplot(3,1,1)
 plot(out);title('Conway Series')
 subplot(3,1,2)
 plot(S(:,1),'r');title('Amplitude Adjusted Surrogate Data')

   %Calculate visibility graph for all series
   [k,logP]=visgraph(out);
   subplot(3,1,3)
   plot(k,logP);hold on;grid on

   for n=1:nS
       [k,logP]=visgraph(S(:,n));
       subplot(3,1,3)
       plot(k,logP,'r');
   end