All Harmonic Analysis and Approximation

Branches that break functions into basic waves and that study how well one class of functions can approximate another. An entry belongs here when its cited source describes Fourier series and transforms, the analysis of signals and groups of symmetries, or the best approximation of a function by polynomials or other simple families. It does not belong here when the branch is chiefly about the general theory of operators or about the measure and integral that underlie all of analysis, which are covered by other groups here. The group links pure theory to applications in signal processing, numerical computation and the study of differential equations.