# ncl_curvp1 man page

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/f…

## Copyright

Copyright (C) 2000

University Corporation for Atmospheric Research

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

## Info

NCAR GRAPHICS March 1998