# ncl_curvp1 - Man Page

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.