Gstat 'polylines' implemented in R?
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 M?nster, Heisenbergstra?e 2, 48149 M?nster, 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>