Category Archives: what-is

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

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What is a Matrix?

A matrix is a rectangular array of numbers on which certain algebraic operations are defined. Matrices provide a convenient way of encapsulating many numbers in a single object and manipulating those numbers in useful ways. An matrix has rows and … Continue reading

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What Is Backward Error?

Backward error is a measure of error associated with an approximate solution to a problem. Whereas the forward error is the distance between the approximate and true solutions, the backward error is how much the data must be perturbed to … Continue reading

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What Is a Condition Number?

A condition number of a problem measures the sensitivity of the solution to small perturbations in the input data. The condition number depends on the problem and the input data, on the norm used to measure size, and on whether … Continue reading

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“What Is” Series

I am starting a series of “What Is” posts. These will give brief descriptions of important concepts in numerical analysis and related areas, with a focus on topics that arise in my research. I will try to adhere to the … Continue reading

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