Function Reference: Volume 3 (P-Z) - The MathWorks - #401

The quantity toi is a tolerance used to demie if a diagonal clement of R is negligible. If [Q,H,E] =qr(A),then

toi - max(size<A))*eps*abs(R(1,1)) The solution >! was computed using the ratiocination and the two steps

y = Q'*b; x = FUy

The computed solution can lie cheeked by forming Ax- '''his equals b to within roundoff error, which indicates that even though the simultaneous equations Ax = b are overdetermined and rank deficient, they happen to be consistent. There are infinitely many solution vectors x; the Q.K lacuiri/at urn has found just one of them.

For inputs of type double, qr uses the LAPACK routines listed in the following tabic to compute (lie QR decomposition.

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