NAME

       CURVPI - integrate a periodic spline curve

SYNOPSIS

       FUNCTION CURVPI (XL, XU, N, X, Y, P, YP, SIGMA)

       This  function calculates an integral between two specified limits.  CURVP1 must be called
       prior to calling CURVPI, and the values thus obtained used as input to CURVPI.  The  value
       of the integral is returned.

DESCRIPTION

       XL          (real, input) The lower limit of the integration.

       XR          (real, input) The upper limit of the integration.

       N           (real, input) The number of input data values. (N > 1)

       X           (real, input) An array containing the abscissae for the input function.

       Y           (real,  input) An array containing the functional values of the input function
                   -- Y(K) is the (real, input) functional value at X(K) for K=1,N.

       P           (real, input) The period of the function.

       YP          (real, input) Contains values for the  second  derivative  (as  calculated  by
                   CURV1).

       SIGMA       (real, input) Tension factor. Values near zero result in a cubic spline; large
                   values (e.g. 50) result in nearly a polygonal line. A typical value is 1.

RETURN VALUE

       CURVPI returns the integral of the interpolated curve between the specified limits.

ACCESS

       To use CURVPI, load the NCAR Graphics library ngmath.

SEE ALSO

       curv1, fitgrid_params.

       Complete documentation for Fitgrid is available at URL
       http://ngwww.ucar.edu/ngdoc/ng/ngmath/fitgrid/fithome.html

COPYRIGHT

       Copyright (C) 2000
       University Corporation for Atmospheric Research

       The use of this Software is governed by a License Agreement.