A review/introduction to principal component analysis and the singular value decomposition -- Lecture notes. (May contain errors, use at your own risk).
Representation using fixed bases (e.g., Wavelets, Fourier Basis, ...) -- Lecture notes on the DFT and on Wavelets. (May contain errors, use at your own risk).
Dimensionality reduction via the Johnson Lindenstrauss Lemma
References:
the textbook "A
mathematical introduction to compressive sensing" by Simon Foucart,
Holger Rauhut (Specifically Chapter 9.5 and parts of Chapters 7 and 8 for probability background)-- and the references and notes therein.