WPchfe WPchia WPchse

WPchia() Function WPchia ( A As  Double, B As  Double, N As  Long, X As  Variant, Y As  Variant, D As  Variant  ) Piecewise Cubic Hermite Integrator, Arbitrary limits Purpose WPchia evaluates the definite integral of a piecewise cubic Hermite function over an arbitrary interval. The interpolant is defined by the coefficients computed by WPchse. Returns Computed approximate value of integral. Parameters [in] A Lower limit of integration. [in] B Upper limit of integration. Note - There is no requirement that [A, B] be contained in [X(0), X(N - 1)]. However, the resulting integral value will be highly suspect, if not. [in] N Number of data points (which were used by Pchse to compute coefficients). (N >= 2) [in] X (N) The data abscissas (which were used by Pchse to compute coefficients). [in] Y (N) The data ordinates (which were used by Pchse to compute coefficients). [in] D (N) An array of cubic spline coefficients computed by Pchse. Reference SLATEC (PCHIP) 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 ----- -------------