NAME

CURVD - derivatives for 1D functions.

SYNOPSIS

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.

DESCRIPTION

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.

RETURN VALUE

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

ACCESS

To use CURVD, load the NCAR Graphics library ngmath.

SEE ALSO

curv1, 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.