# ncl_kurvp2 - Man Page

does interpolation for closed parametric curves

## Synopsis

`CALL KURVP2 (T, XS, YS, N, X, Y, XP, YP, S, SIGMA) `

The interpolated curve is parameterized by mapping points in the interval [0.,1.] onto an interpolated closed 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,Y) and the value 1. is also mapped onto (X,Y), since the interpolated curve is closed. KURVP1 must be called before calling KURVP2.

## 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(1),Y(1)), since the interpolated curve is closed. Any interval [TT,TT+1.] maps onto the entire curve.

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 KURVP1.

YP

(real, input) An array of length N as computed by KURVP1.

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 KURVP2, load the NCAR Graphics library ngmath.