
Recent Posts
Recent Comments
 Nick Higham on Hans Schneider (1927–2014)
 J. M. on 1984 Symposium in Honour of James Wilkinson
 Cleve Moler on 1984 Symposium in Honour of James Wilkinson
 DvH on How Fast is Quadruple Precision Arithmetic?
 Chris Johnson on What Is Rounding?
Categories
 books (18)
 conferences (27)
 Emacs (8)
 LaTeX (14)
 matrix computations (6)
 miscellaneous (14)
 people (15)
 Princeton Companion (12)
 publication peculiarities (7)
 publishing (2)
 research (20)
 software (25)
 whatis (14)
 writing (15)
Monthly Archives: April 2020
What Is Rounding?
Rounding is the transformation of a number expressed in a particular base to a number with fewer digits. For example, in base 10 we might round the number to , which can be described as rounding to three significant digits … Continue reading
What Is a Random Orthogonal Matrix?
Various explicit parametrized formulas are available for constructing orthogonal matrices. To construct a random orthogonal matrix we can take such a formula and assign random values to the parameters. For example, a Householder matrix is orthogonal and symmetric and we … Continue reading
Posted in whatis
Leave a comment
What Is a Correlation Matrix?
In linear algebra terms, a correlation matrix is a symmetric positive semidefinite matrix with unit diagonal. In other words, it is a symmetric matrix with ones on the diagonal whose eigenvalues are all nonnegative. The term comes from statistics. If … Continue reading
Posted in whatis
Leave a comment
What Is a Hadamard Matrix?
A Hadamard matrix is an matrix with elements and mutually orthogonal columns. For example, is a Hadamard matrix. A necessary condition for an Hadamard matrix to exist with is that is divisible by , but it is not known if … Continue reading
Posted in whatis
Leave a comment
What Is an Orthogonal Matrix?
A real, square matrix is orthogonal if (the identity matrix). Equivalently, . The columns of an orthogonal matrix are orthonormal, that is, they have 2norm (Euclidean length) and are mutually orthogonal. The same is true of the rows. Important examples … Continue reading
Posted in whatis
Leave a comment
What Is a Generalized Inverse?
The matrix inverse is defined only for square nonsingular matrices. A generalized inverse is an extension of the concept of inverse that applies to square singular matrices and rectangular matrices. There are many definitions of generalized inverses, all of which … Continue reading
Posted in whatis
3 Comments