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The Walsh Spectrum Logo
on 24 Oct 2021
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% The Walsh spectrum of sloped stripes on the MATLAB logo
% By Victoria A. Sablina
N=256;
r=64;
z=1:N^2;
x=zeros(N)-r+128;
L=logical(mod(ceil(z/3),2));
x(L)=x(L)+2*r;
M=h(N);
X=(x*M)'*M/N^2;
f=log(abs(X)+1);
L=membrane(1,128);
surf(L,f/max(f(:))*255,'EdgeColor','none');
view(-45,20);
colormap(flipud(jet(512)));
axis off;
function m=h(n)
m=[1 1;1 -1];
for i=1:log2(n)-1
m=[m m;m -m];
end
end