avint

avint() void avint ( int  n, double  x[], double  y[], double  a, double  b, double *  result, int *  info  ) Finite interval quadrature for a function with tabulated data (approximation with overlapping parabolas) Purpose This routine 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 there are at least 3 abscissas between the limits of integration. avint also handles two special cases. If the limits of integration are equal, avint returns a result of zero regardless of the number of tabulated values. If there are only two function values, avint uses the trapezoid rule. Parameters [in] n Number of data. (n >= 2) [in] x[] Array x[lx] (lx >= n) Abscissas (strictly in increasing order). [in] y[] Array y[ly] (ly >= n) Ordinates (function values). [in] a Lower limit of integration. (a <= b) [in] b Upper limit of integration. (a <= b) [out] result Computed approximate value of integral. [out] info = 0: Successful exit = -1: The argument n had an illegal value (n < 2) = -4: The argument a (or b) had an illegal value (a > b) = 1: Less than 3 function values between the limits of integration = 2: Abscissas not strictly in increasing order Reference SLATEC