WAvint

WAvint() Function WAvint ( A As  Double, B As  Double, N As  Long, X As  Variant, Y As  Variant  ) Finite interval quadrature for a function with tabulated data (approximation with overlapping parabolas) Purpose WAvint integrates a function tabulated at arbitrarily spaced abscissas. The limits of integration need not coincide with the tabulated abscissas. A method of overlapping parabolas fitted to the data is used provided that thereare at least 3 abscissas between the limits of integration. WAvint also handles two special cases. If the limits of integration are equal, WAvint returns a result of zero regardless of the number of tabulated values. If there are only two function values, WAvint uses the trapezoid rule. Returns Computed approximate value of integral. Parameters [in] A Lower limit of integration. (A <= B) [in] B Upper limit of integration. (A <= B) [in] N Number of data. (N >= 2) [in] X (N) Abscissas. (Must be in increasing order) [in] Y (N) Ordinates (function values). Reference SLATEC Example Using the following table, compute S = integral of 1/(1 + x^2) dx [0, 4] (= atan(4)). x 1/(1 + x^2) ----- ------------- -1 0.5 0 1 1 0.5 2 0.2 3 0.1 4 0.05882 5 0.03846 ----- -------------