Charles William Clenshaw

Charles William Clenshaw, who lived from 15 March 1926 to 23 September 2004, was an English mathematician who specialized in numerical analysis. He is known for the Clenshaw algorithm of 1955 for summing Chebyshev series and for Clenshaw-Curtis quadrature of 1960, a method of numerical integration on an automatic computer. In a 1984 paper, Beyond Floating Point, he and Frank W. J. Olver introduced symmetric level-index arithmetic. From 1945 to 1969 he was a mathematician at the National Physical Laboratory in Teddington, where he headed the numerical methods group from 1961, and in 1969 he became professor of numerical analysis at Lancaster University, where he helped strengthen the mathematics department and later became professor emeritus. His research covered approximation theory based on Chebyshev polynomials, software for trigonometric and Bessel functions, and computer arithmetic systems.