NAME

       CURVP1 - calculate values for CURVP2 usage.

SYNOPSIS

       CALL CURVP1 (N, X, Y, P, YP, TEMP, SIGMA, IER)

       This  subroutine  calculates certain values that are used by CURVP2 in order to compute an
       interpolatory spline under tension through a sequence of functional values for a  periodic
       function. The actual computation of the interpolated values must be done using CURVP2 .

DESCRIPTION

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

       P           (real, input) The period of the function. P must be greater than X(N)-X(1).

       YP          (real, output) Contains values for the second derivative (these are calculated
                   by CURVP1).

       TEMP        (real, input) Scratch space.

       SIGMA       (integer,  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.

       IER         (integer,  output)  An  error  return  value. If IER is returned as 0, then no
                   errors were detected.

                   = 1 if N is less than 2.
                   = 2 if P is less than or equal to X(N)-X(1).
                   = 3 if the X values are not strictly increasing.

ACCESS

       To use CURVP1, load the NCAR Graphics library ngmath.

SEE ALSO

       curvp2, 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.