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More generally, we can factor a complex m×n matrix A, with m ≥ n, as the product of an m×m unitary matrix Q and an m×n upper triangular matrix R.As the bottom (m−n) rows of an m×n upper triangular matrix consist entirely of zeroes, it is often useful to partition R, or both R and Q:
Instead, the QR algorithm works with a complete basis of vectors, using QR decomposition to renormalize (and orthogonalize). For a symmetric matrix A , upon convergence, AQ = QΛ , where Λ is the diagonal matrix of eigenvalues to which A converged, and where Q is a composite of all the orthogonal similarity transforms required to get there.
An RRQR factorization or rank-revealing QR factorization is a matrix decomposition algorithm based on the QR factorization which can be used to determine the rank of a matrix. [1] The singular value decomposition can be used to generate an RRQR, but it is not an efficient method to do so. [2] An RRQR implementation is available in MATLAB. [3]
The meaning of the composition of two Givens rotations g ∘ f is an operator that transforms vectors first by f and then by g, being f and g rotations about one axis of basis of the space. This is similar to the extrinsic rotation equivalence for Euler angles.
In the theory of Lie group decompositions, it is generalized by the Iwasawa decomposition. The application of the Gram–Schmidt process to the column vectors of a full column rank matrix yields the QR decomposition (it is decomposed into an orthogonal and a triangular matrix).
For the QR algorithm with a reasonable target precision, this is , whereas for divide-and-conquer it is . The reason for this improvement is that in divide-and-conquer, the Θ ( m 3 ) {\displaystyle \Theta (m^{3})} part of the algorithm (multiplying Q {\displaystyle Q} matrices) is separate from the iteration, whereas in QR, this must occur in ...
QR decomposition, a decomposition of a matrix QR algorithm, an eigenvalue algorithm to perform QR decomposition; Quadratic reciprocity, a theorem from modular arithmetic; Quasireversibility, a property of some queues; Reaction quotient (Q r), a function of the activities or concentrations of the chemical species involved in a chemical reaction
At the very beginning of the page, there is a mistake: "In linear algebra, a QR decomposition, also known as a QR factorization or QU factorization, is a decomposition of a matrix A into a product A = QR of an orthogonal matrix Q and an upper triangular matrix R." I think it's worth noting that Q is only orthogonal if it's square.