I am trying to run a forest fire simulation. However, when I run the following code in Matlab, the plot window is blank. What do i do?

This is the code:

     function y = fire_sim(N,p)

     figure(1);

     %sets size of forest NxN
     C = ones(N,N);
     Z = zeros(N,N);
     x = 1:N;
     y = 1:N;

     %Set initial fire
     fires = [floor(N/2),floor(N/2)];
     [numfires,temp] = size(fires);

     for i = 1:numfires
         C(fires(i,1),fires(i,2))=2;
     end

     %Simulate spread
     maxsteps = 1000; %number of iterations to plot
     k=0;

     while k<maxsteps && numfires>0
         lastC = C;
         numfires_next = 0;
         fires_next = [];

         for i = 1:numfires
             if fires(i,1)~=1
                 if C(fires(i,1)-1,fires(i,2))==1
                     r = rand(1);
                     if r < p
                         numfires_next = numfires_next + 1;
                         C(fires(i,1)-1,fires(i,2))=2;
                         fires_next(numfires_next,:)=[fires(i,1)-1,fires(i,2)];
                     end
                 end
             end
             if fires(i,1)~=N
                 if C(fires(i,1)+1,fires(i,2))==1
                     r = rand(1);
                     if r < p
                         numfires_next = numfires_next + 1;
                         C(fires(i,1)+1,fires(i,2))=2;
                         fires_next(numfires_next,:)=[fires(i,1)+1,fires(i,2)];
                     end
                 end
             end
             if fires(i,2)~=1
                 if C(fires(i,1),fires(i,2)-1)==1
                     r = rand(1);
                     if r < p
                         numfires_next = numfires_next + 1;
                         C(fires(i,1),fires(i,2)-1)=2;
                         fires_next(numfires_next,:)=[fires(i,1),fires(i,2)-1];
                     end
                 end
             end
             if fires(i,2)~=N
                 if C(fires(i,1),fires(i,2)+1)==1
                     r = rand(1);
                     if r < p
                         numfires_next = numfires_next + 1;
                         C(fires(i,1),fires(i,2)+1)=2;
                         fires_next(numfires_next,:)=[fires(i,1),fires(i,2)+1];
                     end
                 end
             end
             C(fires(i,1),fires(i,2))=0;
         end
         surf(x,y,C,C);
         view(360,90);
         colormap([0 0 0; 0 1 0; 1 0 0])
         caxis([0 2]);
         axis([1,length(x),1,length(y),0,2])
         shading interp
         title(sprintf('Step = %.0f',k))
         drawnow;
         k=k+1;
         if sum(sum(abs(lastC-C)))==0
              break
         end

         fires = fires_next;

         numfires = numfires_next;

     end

Answer 1

[Walter Roberson]

The code works for me in R2014a. Run it like

fire_sim(300,.5);

A parameter of .5 creates some nice designs about half the runs (and dies out quickly the other half of the runs.)

[Lakshmi K]

Thank you!!

[Alex chavez]

Hello, I tried this fix and it worked but only for the 2-D version but I could not figure out how to run the 3-D version of the forest fire. When I try to run it I get a blank graph and this error message: Error using fire_sim(line 4) Not enough input arguments. My line 4 looks like this C = ones(N,N);

[Walter Roberson]

Change

       C = ones(N,N);

to

       if ~exist(N, 'var'); N = 300; fprintf('Defaulting to 300 x 300. Next time, pass the size as the first parameter. Do not just click Run, use the command line.\nDo not just click Run, use the command line.\nLike fire_sim(300, .5); at the command line.'); end
       if ~exist(p, 'var'); p = 0.5; fprintf('Defaulting to p = 0.5. Next time, pass the probability as the parameter. \n'); end
       C = ones(N,N);

[Karri Rama]

@walter

I used fire_sim(300,.5)

I am not getting 3D plot, but getting nice 2D plot..

what changes should i make to get 3D plot

Answer 2

[Alex chavez]

What is this for loop doing since numfires equals one and what is actually happening inside the loop with this line "C(fires(i,1),fires(i,2))=2;"?

    for i = 1:numfires

         C(fires(i,1),fires(i,2))=2;

     end

[Image Analyst]

I answered that in your other thread: https://www.mathworks.com/matlabcentral/answers/344976-what-is-this-for-loop-doing-since-numfires-equals-one-and-what-is-actually-happening-inside-the-loop#answer_270871 before I knew you also asked it here. So read it there.

Answer 3

[Aaron Staszewski]

im trying to do something similar and was wondering how / which lines of code made sure that the red fire dots did not spread back over the already burnt grey area?