# 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[1],Y[1]) and the value 1. is also mapped onto (X[1],Y[1]), 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.