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% illustration of an indicator function in two dimensionsfunctionmain()% the number of data points. More points means prettier picture.N=400;% a function close to what we want, but not smoothZ=get_step_function(N);% plot the surfacefigure(2);clf;holdon;axisequal;axisoff;scale=100;surf(scale*Z);% make the surface beautifulshadinginterp;colormapautumn;% add in a source of lightcamlight(-50,54);% viewing angleview(-40,38);% save as pngprint('-dpng','-r200','Indicator_function_illustration.png');% get a function which is 1 on a set, and 0 outside of itfunctionZ=get_step_function(N)XX=linspace(-1.5,4,N);YY=linspace(-4,4,N);[X,Y]=meshgrid(XX,YY);c=2;k=1.2;shift=10;Z=(c^2-X.^2-Y.^2).^2+k*(c-X).^3-shift;Z=1-max(sign(Z),0);
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{{Information |Description=Illustration of an en:Indicator function. |Source=self-made with MATLAB, source code below |Date=~~~~~ |Author= Oleg Alexandrov }} <pre><nowiki> % illustration of an indicator function in two dime