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The singular value decomposition is very general in the sense that it can be applied to any matrix, whereas eigenvalue decomposition can only be applied to square diagonalizable matrices. Nevertheless, the two decompositions are related.
Let A be a square n × n matrix with n linearly independent eigenvectors q i (where i = 1, ..., n).Then A can be factored as = where Q is the square n × n matrix whose i th column is the eigenvector q i of A, and Λ is the diagonal matrix whose diagonal elements are the corresponding eigenvalues, Λ ii = λ i.
The smallest singular value of a matrix A is σ n (A). It has the following properties for a non-singular matrix A: The 2-norm of the inverse matrix (A −1) equals the inverse σ n −1 (A). [2]: Thm.3.3 The absolute values of all elements in the inverse matrix (A −1) are at most the inverse σ n −1 (A). [2]: Thm.3.3
Applicable to: square, complex, non-singular matrix A. [5] Decomposition: =, where Q is a complex orthogonal matrix and S is complex symmetric matrix. Uniqueness: If has no negative real eigenvalues, then the decomposition is unique. [6]
The truncation of a matrix M or T using a truncated singular value decomposition in this way produces a truncated matrix that is the nearest possible matrix of rank L to the original matrix, in the sense of the difference between the two having the smallest possible Frobenius norm, a result known as the Eckart–Young theorem [1936].
The 2-norm of a matrix A is the norm based on the Euclidean vectornorm; that is, the largest value ‖ ‖ when x runs through all vectors with ‖ ‖ =. It is the largest singular value of . In case of a symmetric matrix it is the largest absolute value of its eigenvectors and thus equal to its spectral radius.
The singular value decomposition of a matrix is = where U and V are unitary, and is diagonal.The diagonal entries of are called the singular values of A.Because singular values are the square roots of the eigenvalues of , there is a tight connection between the singular value decomposition and eigenvalue decompositions.
Truncated singular value decomposition (SVD) in numerical linear algebra can also use the Rayleigh–Ritz method to find approximations to left and right singular vectors of the matrix of size in given subspaces by turning the singular value problem into an eigenvalue problem.