NAME

       CURVP2 - interpolate a periodic function at a specified point

SYNOPSIS

       FUNCTION CURVP2 (T, N, X, Y, P, YP, SIGMA)

       This  function  interpolates  a  value  at a specified point using a spline under tension.
       CURVP1 must be called prior to calling CURVP2, and the values thus obtained used as  input
       to CURVP2. CURVP2 returns the interpolated function value at the X-coordinate specified.

DESCRIPTION

       T           (real,  input)  The  abscissa  for  which  an  interpolated  function value is
                   desired.

       N           (integer, 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  data  --
                   Y(K) is the functional value at X(K) for K=1,N.

       X           (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

       CURVP2 returns the interpolated value at the specified point T.

ACCESS

       To use CURVP2, load the NCAR Graphics library ngmath.

SEE ALSO

       curvp1, 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.