[R-sig-eco] multivariate smoothing and gradient estimation

[Dave Roberts]

Chris,

     One (sub-optimal) solution would be to fit GAMS and then have the 
gam.predict estimate values immediately near your data points which you 
could use to calculate a local gradient.  If the GAM is reasonably 
smooth, I would think you could get estimates that were reasonable.

Dave
-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
David W. Roberts                                     office 406-994-4548
Professor and Head                                      FAX 406-994-3190
Department of Ecology                         email droberts at montana.edu
Montana State University
Bozeman, MT 59717-3460

Chris Martin wrote:
> Dear list members,
> 
> I am a looking for a function that can calculate a "surface" from at least
> four predictor variables and one response variable. I would then like to
> calculate the first derivative of a specific point on this surface.
> 
> I have looked at many packages for nonparametric smoothing and kernel
> density estimation but have been unable to find any that fulfill both these
> criteria. For example, loess can handle multivariate data, but I do not how
> to extract the derivative from the resulting fit? Many smoothing splines
> offer predict functions to extract the derivative, but these functions can
> only handle univariate data (e.g. smooth.spline). Ideally, I would like to
> use local estimates of the surface (i.e. loess).
> 
> I would appreciate any suitable functions or advice on where to look for
> functions that fulfill both these criteria.
> 
> Thank you very much for your time.
> 
> best wishes,
> Chris Martin
> Population Biology Graduate Group '12
> University of California, Davis
> 
> 	[[alternative HTML version deleted]]
> 
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