curvd (3NCARG)

FUNCTION CURVD (T, N, X, Y, YP, SIGMA)

This function calculates a derivative at a specified point using a spline under tension. CURV1 must be called prior to calling CURVD, and the values thus obtained used as input to CURVD. The derivative value is returned.

T

(real, input) The abscissa for which an interpolated function value is desired.

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 data -- Y(K) is the functional value at X(K) for K=1,N.

YP

(real, input) Contains values for the second derivative (as calculated by CURV1).

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.

CURVD returns the derivative value of the interpolated curve at the specified point T.

To use CURVD, load the NCAR Graphics library ngmath.

curv1, fitgrid_params.

Complete documentation for Fitgrid is available at URL

http://ngwww.ucar.edu/ngdoc/ng/ngmath/fitgrid/fithome.html

Copyright (C) 2000

University Corporation for Atmospheric Research

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