Resumen: The stability of the representation of finite rank operators in terms of a basis is analyzed. A conditioning is introduced as a measure of the stability properties. This conditioning improves some other conditionings because it is closer to the Lebesgue function. Improved bounds for the conditioning of the Fourier sums with respect to an orthogonal basis are obtained, in particular, for Legendre, Chebyshev, and disk polynomials. The Lagrange and Newton formulae for the interpolating polynomial are also considered. Idioma: Inglés DOI: 10.1007/s10444-023-10057-9 Año: 2023 Publicado en: ADVANCES IN COMPUTATIONAL MATHEMATICS 49, 4 (2023), 52 [33 pp.] ISSN: 1019-7168 Factor impacto JCR: 1.7 (2023) Categ. JCR: MATHEMATICS, APPLIED rank: 83 / 332 = 0.25 (2023) - Q1 - T1 Factor impacto CITESCORE: 3.0 - Computational Mathematics (Q2) - Applied Mathematics (Q2)