Stieltjes Integral
Stieltjes integral
[′stēlt·yəs ‚int·ə·grəl]Stieltjes Integral
a generalization of the definite integral proposed in 1894 by T. Stieltjes. In this generalization, the limit of the Riemann sums ∑f(ξi)(xi – xi-1) is replaced by the limit of the sums ∑f(ξi) [Φ(xi) – Φ(xi-1)]. where the integrating function ϕ(x) is a function of bounded variation (seeVARIATION OF A FUNCTION). If ϕ(x) is differentiable, then the Stieltjes integral can be expressed in terms of the Riemann integral (if it exists):