[R-sig-Geo] experimental covariogram

[Edzer Pebesma]

On 22/06/16 16:15, Nick Perpinias wrote:
> Dear R-GIS users,
> 
> I am trying to do a performance evaluation/comparison between the
> covariogram and semivariogram for certain spatially correlated data.
> In particular, I would like to investigate if there is a certain trade off
> using either of these two tools when for example there is no trend on the
> spatial field.
> 
> Although checking the main packages for spatial statistics in R (sp,
> spatstat, geoR, geoRglm, gstat) I wasn't able to find a function
> calculating the experimental covariogram of a given spatial dataset.

I don't think that sp or spatstat bring you anything in this respect.

gstat::variogram computes the covariogram when asked; the code that
(finally) does it is here:

https://github.com/edzer/gstat/blob/master/src/sem.c#L342

> 
> In geoRglm there is only a very specific implementation for covariogram
> estimation (covariog function) and in gstat packet the variogram function
> has the option of covariogram without making clear if the covariogram is
> computed or extracted from the semivariogram.
> 
> I would be grateful if you could point out an existing function of a plan
> of attack for my question.

I'd be interested in learning why you think this is important.

> 
> Thank you in advance for your time and help.
> 
> Best Regards,
> 
> Nikos
> 
> 	[[alternative HTML version deleted]]
> 
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-- 
Edzer Pebesma
Institute for Geoinformatics  (ifgi),  University of Münster
Heisenbergstraße 2, 48149 Münster, Germany; +49 251 83 33081
Journal of Statistical Software:   http://www.jstatsoft.org/
Computers & Geosciences:   http://elsevier.com/locate/cageo/
Spatial Statistics Society http://www.spatialstatistics.info

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