% QR•ª‰ð�i”ñ�³‘¥�s—ñ�j

A = [ 0,  0,  0; ...
      1,  2,  2;
      2,  4,  1 ];

[Q,R,index] = qr(A,0);
n = rank(R);
P = Q(:,1:n)*Q(:,1:n)';

fprintf("�s—ñ P ‚Æ PA\n");
P
P*A
