Results for: Numerical Analysis

Latent Semantic Indexing, SVD, and Zipf’s Law 5

Posted by Cleve Moler,

Latent Semantic Indexing, LSI, uses the Singular Value Decomposition of a term-by-document matrix to represent the information in the documents in a manner that facilitates responding to queries and other information retrieval tasks. I set out to learn for myself how LSI is implemented. I am finding that it is harder than I thought.... read more >>

Householder Seminar HHXX on Numerical Linear Algebra 2

Posted by Cleve Moler,

The Householder meetings on Numerical Linear Algebra have been held roughly every three years since 1961. The twentieth, with the logo HHXX, was held June 18th through 23rd at Virginia Tech in Blacksburg, Virginia. I've been to 17 of the meetings. They have been an important part of my professional life and I've written Cleve's Corner articles and blog posts about them, MathWorks News & Notes, and Householder XIX.... read more >>

Ulps Plots Reveal Math Function Accuracy 2

Posted by Cleve Moler,

"ULP" stands for "unit in the last place." An ulps plot samples a fundamental math function such as $\sin{x}$, or a more esoteric function like a Bessel function. The samples are compared with more accurate values obtained from a higher precision computation. A plot of the accuracy, measured in ulps, reveals valuable information about the underlying algorithms.... read more >>