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The solutions to homework 6 for the cs 417/517 computational methods and software course offered in spring 2004. It includes the matrix of normal equations, the right hand vector of normal equations, the cholesky factor, and the least squares solution. The document also demonstrates the qr decomposition and the orthogonality of the matrix c.
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Spring 2004 Solutions to HW 6 Assigned: Thurs Mar 25, 2004; Due: Thurs Apr 1, 2004
.
Right hand vector of normal equations = A′^ ∗ b
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Cholesky factor is chol(A′^ ∗ A)
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Least squares solution is (^)
.
x =
.
(b) The System QRx ≈ b [Q R] = qr(A) Q = (^)
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and R = (^)
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So (^)
x^ =^ Q′^ ∗^ b^ =
.
(c) x = (^) (
) .
(a) (Q 1 ∗ Q 2 ) ∗ (Q 1 ∗ Q 2 )T^ = (Q 1 ∗ Q 2 ) ∗ (QT 2 ∗ QT 1 ) = Q 1 ∗ (Q 2 ∗ QT 2 ) ∗ QT 1 = Q 1 ∗ I ∗ QT 1 = Q 1 ∗ QT 1 = I
(b) Since ‖Qv‖ 2 = ‖v‖ 2 then ‖Q‖ 2 = 1
Since ‖Q−^1 ‖ 2 = ‖Q‖ 2 = 1 then cond(Q) = 1