%% Sunspot data

load sunspot.dat
npts=288;
t=sunspot(:,1); x=sunspot(:,2);
plot(t,x);
meansun=mean(x);
x=x-meansun;

% Create a circulant matrix from the time series
X=zeros(npts,npts);
idx=1:npts;

for j=2:npts
    idx=[idx(npts) idx(1:npts-1)];
    X(:,j)=x(idx);
end


%% Analyze the circulant matrix
[U,S,V]=svd(X);
ss=diag(S)./sum(diag(S));