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?
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Lakshmi K
il 6 Mar 2016
Risposto: Aaron Staszewski
il 26 Mar 2020
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
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Risposta accettata
Walter Roberson
il 6 Mar 2016
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.)
4 Commenti
Walter Roberson
il 11 Mag 2017
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
il 21 Nov 2019
@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
Più risposte (2)
Alex chavez
il 16 Giu 2017
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
1 Commento
Image Analyst
il 16 Giu 2017
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.
Aaron Staszewski
il 26 Mar 2020
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?
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