[R] 2D interpolation function
Prof Brian Ripley
ripley at stats.ox.ac.uk
Tue May 22 14:25:45 CEST 2001
On Tue, 22 May 2001, Jim Lemon wrote:
> As part of a project I am doing, I had to present a 2D table as a
> surface. This was fairly straightforward (using persp), but I needed to
> interpolate points to make it sort of pretty. This was done by using
> quadratic interpolation between the existing points to smooth out the
> surface a bit. As I couldn't find an R function that did this, I wrote
> an admittedly nasty pair of functions that will interpolate any
> reasonable number of equally spaced points between the values of an
> object produced by table(), smoothed with any reasonable power function
> of the distance. In practice, this means I tested it with up to four or
> five interpolated points up to a cubic interpolation.
> If anyone is interested in telling me:
> a) I overlooked an existing function (p~0.95)
package akima contains functions that will do a better job than
distance-based interpolation. You could also use kriging (spatial,
> b) This would be a useful function for them (p~0.01)
> I would be happy to hear about it.
> PS - I assumed that the remaining 0.04 would be the probability that no
> one was interested.
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Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
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