Monday, June 25, 2007

Matlab: Mandelbrot set

Recently I read article on Free Software Magazine titled Generating cool fractals. I was very pleased to find source code for generation of Mandelbrot set.
function mandelFrac
% MATLAB and Octave code to generate
%a Mandelbrot fractal

% Number of points in side of image and
% number of iterations in the Mandelbrot
% fractal calculation
npts=1000;
niter=51;
% Generating z = 0 (real and
% imaginary part)
zRe=zeros(npts,npts);
zIm=zeros(npts,npts);
% Generating the constant k (real and
% imaginary part)
kRe=repmat(linspace(-1.5,0.5,npts),npts,1);
kIm=repmat(linspace(-1,1,npts)',1,npts);

% Iterating
for j=1:niter
% Calculating q = z*z + k in complex space
% q is a temporary variable to store the result
qRe=zRe.*zRe-zIm.*zIm+kRe;
qIm=2.*zRe.*zIm+kIm;
% Assigning the q values to z constraining between
% -5 and 5 to avoid numerical divergences
zRe=qRe;
qgtfive= find(qRe > 5.);
zRe(qgtfive)=5.;
qltmfive=find(qRe<-5.);
zRe(qltmfive)=-5.;
zIm=qIm;
hgtfive=find(qIm>5.);
zIm(hgtfive)=5.;
hltmfive=find(qIm<-5.);
zIm(hltmfive)=-5.;
end

% Lines below this one are commented out when making
% the benchmark.

% Generating plot
% Generating the image to plot
ima=log( sqrt(zRe.*zRe+zIm.*zIm) + 1);
% Plotting the image
imagesc(ima);

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