X=[
1.1	1.1	1.2
1.2	1.4	1.2
1.3	1.2	1.6
1.5	1.4	1.5
1.6	1.8	1.6
1.9	1.7	1.9
1.9	2	2.2
2.3	2.2	2.1
2.4	2.5	2.4
2.5	2.2	2.3];
X=[ones(10,1) X];
y=[22.3
22.1
24.6
24.2
26.8
30.3
32.7
32.3
32.8
32.6];
PRESS=zeros(4,1);
for N=1:4
for i=1:10
  Xc=X;
  Xc(i,:)=[];
  yc=y;
  yc(i,:)=[];
  [S D]=eigs(Xc'*Xc);
  Sr=S(:,1:N);
  Dr=D(1:N,1:N);
  tetarc=Sr*inv(Dr)*Sr'*Xc'*yc;
  PRESS(N)=PRESS(N)+(y(i)-X(i,:)*tetarc)^2;
end
end
PRESS