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Singular Value Decomposition
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Applications of SVD
SVD is used in signal processing, data reduction, solving inverse problems, and principal component analysis among other applications.
SVD for Image Compression
In image compression, SVD can reduce the amount of information needed to reconstruct an image by keeping only a few of the largest singular values and corresponding singular vectors, significantly reducing the data size without substantial quality loss.
Diagonal Matrix in SVD
The diagonal matrix in SVD contains the singular values, which are the lengths of the semi-axes of the ellipsoid represented by the matrix , ordered from largest to smallest.
Full SVD vs Reduced SVD
Full SVD includes all the singular values (including zeros) and corresponding vectors, resulting in and matrices of size equal to the original matrix. In contrast, reduced SVD omits the zero singular values and the corresponding vectors.
SVD and Pseudoinverse
The pseudoinverse of a matrix , denoted , can be computed using SVD by taking where is formed by taking the reciprocal of the non-zero singular values of and transposing the matrix.
Compact SVD
Compact SVD is a variant of SVD where matrices and are truncated to include only the columns corresponding to the non-zero singular values, often used when the matrix has more zero singular values.
Unitary Matrices in SVD
In SVD, and are unitary matrices, meaning they satisfy and , where is the identity matrix and * denotes the conjugate transpose operation.
SVD Equation
The equation for SVD of a matrix is , where and are orthogonal (or unitary, if complex) matrices, is a diagonal matrix, and is the conjugate transpose of .
Definition of SVD
Singular Value Decomposition is a factorization of a matrix into three matrices , , and , where and are unitary matrices and is a diagonal matrix containing the singular values.
Relation between SVD and Eigen-decomposition
SVD is related to eigen-decomposition in that the singular values of are the square roots of the eigenvalues of or , and the columns of and are the eigenvectors of and respectively.
SVD of a Rectangular Matrix
SVD can be applied to any rectangular matrix, not just square matrices. The resulting , , and matrices will have dimensions , , and respectively in the full SVD case.
Stability of SVD
SVD is numerically stable, meaning small changes in the input matrix will cause only small changes in the singular values and singular vectors. This makes SVD a reliable method for numerical computations.
Singular Values
Singular values are the non-negative values on the diagonal of matrix in the SVD. They are the square roots of the nonzero eigenvalues of where is the original matrix.
SVD for Matrix Rank Determination
The rank of a matrix can be determined using SVD by counting the number of non-zero singular values in . This corresponds to the number of linearly independent rows or columns in .
Eckart-Young Theorem
The Eckart-Young theorem states that the best low-rank approximation of a matrix can be obtained by using the SVD and setting all but the largest singular values in to zero, forming .
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