# ncl_kurv2 - Man Page

does interpolation for parametric curves

## Synopsis

`CALL KURV2 (T, XS, YS, N, X, Y, XP, YP, S, SIGMA) `

The interpolated curve is parameterized by mapping points in the interval [0.,1.] onto the interpolated curve. The resulting curve has a parametric representation both of whose components are splines under tension and functions of the polygonal arc length. The value 0. is mapped onto (X[1],Y[1]) and the value 1. is mapped onto (X[N],Y[N]). KURV1 must be called before calling KURV2.

## Description

- T
(real, input) A value to be mapped to a point on the curve. The interval [0.,1.] is mapped onto the curve such that 0. is mapped to (X(1),Y(1)) and 1. is mapped to (X(N),Y(N)). Values outside of [0.,1.] result in extrapolation.

- XS
(real, oputput) Contains the X coordinate of the interpolated point that T maps to.

- YS
(real, oputput) Contains the Y coordinate of the interpolated point that T maps to.

- N
(integer, input) The number of input data points. (N > 1)

- X
(real, input) An array containing the X values of the input points.

- Y
(real, input) An array containing the Y values of the input points. Adjacent pairs of points must be distinct.

- XP
(real, input) An array of length N as computed by KURV1.

- YP
(real, input) An array of length N as computed by KURV1.

- S
(real, input) An array of length N containing the polygonal arc lengths of the curve.

- 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.

## Access

To use KURV2, load the NCAR Graphics library ngmath.

## See Also

kurv1, 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.