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Topic: Re: BUG or FEATURE in Interpolation[] ?
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Harald Berndt

Posts: 24
Registered: 12/7/04
Re: BUG or FEATURE in Interpolation[] ?
Posted: Aug 16, 1996 2:59 AM
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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

Harald Berndt University of California
Research Specialist Forest Products Laboratory
Phone: 510-215-4224 FAX:510-215-4299

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