Help with an infection simulation?

Hi,

I'm trying to create a simulation of an infection spreading. I have the code for a spatial view of the spread, just on a grid. Now, I'm trying to put that on a map of the world. I think that geoshow might be the best bet in creating that, but I'm not sure about how to go about that.

I've attached my code for the original. I've been playing around with the simulation on the world map, but I really dont know what direction I should be headed in:

close all clear all

figure; worldmap world load coast plotm(lat, long) geoshow('landareas.shp','Facecolor',[0.5 0.7 0.5]) set(gcf,'double','on') hold on

dt=0.1; t1=10; time=0:dt:t1; a=0.5;b=1;ratio=a/b;

N=101;L=50; latgrid=ones(N,1)*linspace(-L,L,N); longrid=linspace(-L,L,N)'*ones(1,N); state=zeros(N,N); % state(i,j)=1 infected; -1 recoverd; 0 susceptible

%initial geoshow(

Nstep=length(time); S=zeros(1,Nstep); % total number of S, I, R at each time step I=zeros(1,Nstep); R=zeros(1,Nstep); S(1)=length(find(state==0)); I(1)=length(find(state==1)); R(1)=length(find(state==-1));

k=1; for t=dt:dt:t1 k=k+1; th=conv2(double(state>0),ones(3,3),'same'); % count # of infected in neighbor SI_ind=find(rand(size(S_ind))<th(S_ind)*a*dt); IR_ind=find(rand(size(I_ind))<b*dt); state(S_ind(SI_ind))=1; % S -> I state(I_ind(IR_ind))=-1;

    S(k)=length(find(state==0));
    I(k)=length(find(state==1));
    R(k)=length(find(state==-1));

    I_ind=find(state==1); % I
    set(h1,'xdata',Xgrid(I_ind),'ydata',Ygrid(I_ind));
    S_ind=find(state==0); % S
    set(h2,'xdata',Xgrid(S_ind),'ydata',Ygrid(S_ind));
    R_ind=find(state==-1);% R
    set(h3,'xdata',Xgrid(R_ind),'ydata',Ygrid(R_ind));
    drawnow;

    geoshow(xdata,ydata,'DisplayType',surface)
end

figure; plot(time,[S;I;R])

Thanks!