[R-sig-Geo] Gstat 'polylines' implemented in R?

[Edzer Pebesma]

On 09/04/2015 06:31 AM, Tim Peterson wrote:
> Hi all,
> 
> I'm keen to use the gstat feature 'polylines' (appendix B in 
> http://www.gstat.org/gstat.pdf) to restrict the point sample selection 
> to within a polygon. That is, when undertaking localised kriging at a 
> grid cell, samples are only used in the estimation if a line between the 
> sample and grid cell does not cross a polygon boundary. The polylines 
> feature appears to be implemented within the c-code for gstat 
> (polygon.c) but I cannot find any means to use it within R-gstat nor any 
> mention on lists. Any tips would be most welcome.

That is correct, it has not been interfaced from the R code.

The idea is nice, but if you work with it you see very very much
unwanted features in the interpolated surface: sharp edges that follow
the "shadow" of the polygon, as seen from an observation with an extreme
value. Back then we thought about a work-around for this using distances
measured "around" the obstacles, but that leads to non-positive definite
covariance functions.

> 
> Thanks,
> 
> Tim
> 
> ----------------------
> Dr. Tim Peterson
> 
> The Department of Infrastructure Engineering
> The University of Melbourne, 3010 Australia
> T: +61 3 8344 9950 <tel:%2B61%203%208344%209950>, M: +61 0438 385 937 
> <tel:%2B61%200438%20385%20937>
> 
> Dept. profile : 
> http://www.ie.unimelb.edu.au/people/staff.php?person_ID=141135
> Research Gate : https://www.researchgate.net/profile/Tim_Peterson7
> Google Scholar: 
> http://scholar.google.com.au/citations?user=kkYJLF4AAAAJ&hl=en&oi=ao
> 
> 	[[alternative HTML version deleted]]
> 
> _______________________________________________
> R-sig-Geo mailing list
> R-sig-Geo at r-project.org
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
> 

-- 
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

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 490 bytes
Desc: OpenPGP digital signature
URL: <https://stat.ethz.ch/pipermail/r-sig-geo/attachments/20150904/5df6a708/attachment.bin>