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
am 6 Mär. 2016
Beantwortet: Aaron Staszewski
am 26 Mär. 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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Akzeptierte Antwort
Walter Roberson
am 6 Mär. 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 Kommentare
Walter Roberson
am 11 Mai 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
am 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
Weitere Antworten (2)
Alex chavez
am 16 Jun. 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 Kommentar
Image Analyst
am 16 Jun. 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
am 26 Mär. 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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