Stefan Schulz wrote: > ... > I found to my surprise, that the function returned by Interpolation > is not smooth at some of the data points!
Well, it is documented: The Book says that the approximated function varies smoothly between sample points, nothing about smoothness of derivatives at sample points. And if you set InterpolationOrder -> 1, you get just plain linear interpolation.
>For this reason I resorted to > write a package Spline1D which returns a smooth cubic spline as a > pure function, but is naturally slower than the built-in Interpolation > command.
You could probably have used the "Graphics`Spline`" standard package.
>Did I find a bug or is this a feature? If it is a feature > it certainly makes the Interpolation command not suitable to obtain > smooth curves.
There's also InterpolatingPolynomial (which returns something you probably don't want in your particular example) and of course Fit or NonlinearFit.
-- _______________________________________________________________ Harald Berndt University of California Research Specialist Forest Products Laboratory Phone: 510-215-4224 FAX:510-215-4299 _______________________________________________________________