[R-sig-Geo] Spacetime regression
Hi all, I want to do a spatio-temporal regression on a quite large dataset. I have 100 k records. These correspond to measurements taken at 3000 locations, approximately every half year. The geographic area is all of the Netherlands (240 x 300 km). Is spatio-temporal kriging advisable for a dataset that is so large? When I make the sample space-time variogram (with variogramST), it automatically chooses a time-lag difference of about 2 days. This is much too small to be meaningful for my data; half-year periods would be interesting. Is there a way to tell this to the variogramST function? Thanks in advance, Roelof Coster [[alternative HTML version deleted]] ___ R-sig-Geo mailing list R-sig-Geo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo
[R-sig-Geo] New glcm package for calculating co-occurrence textures now on CRAN
Hi all, I just released the new glcm package to CRAN. The glcm package enables calculating image textures derived from grey-level co-occurrence matrices (GLCMs) in R. The underlying texture calculation code is implemented in C++ using RcppArmadillo. I have tested the calculated textures versus other implementations, but let me know if you notice anything unexpected. Also, I just pushed out another package to CRAN that may be of interest to some in this group. The wrspathrow package has several functions for working with path and row numbers from the World Reference System (WRS, the system used by NASA for the Landsat satellites). The package supports calculating the path(s) and row(s) needed to cover a given sp or raster object, or, conversely, can calculate the polygon for a given path and row. Cheers, Alex -- Alex Zvoleff Postdoctoral Associate Tropical Ecology Assessment and Monitoring (TEAM) Network Conservation International 2011 Crystal Dr. Suite 500, Arlington, Virginia 22202, USA Tel: +1-703-341-2749, Fax: +1-703-979-0953, Skype: azvoleff http://www.teamnetwork.org | http://www.conservation.org ___ R-sig-Geo mailing list R-sig-Geo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo
Re: [R-sig-Geo] Spacetime regression
On 02/13/2014 01:30 PM, Roelof Coster wrote: Hi all, I want to do a spatio-temporal regression on a quite large dataset. I have 100 k records. These correspond to measurements taken at 3000 locations, approximately every half year. The geographic area is all of the Netherlands (240 x 300 km). Sample variograms are a quadratic form, meaning that all pairs of your 100K records are evaluated; that makes 10^10 pairs. Are you a patient person? Is spatio-temporal kriging advisable for a dataset that is so large? When I make the sample space-time variogram (with variogramST), it automatically chooses a time-lag difference of about 2 days. This is much too small to be meaningful for my data; half-year periods would be interesting. Is there a way to tell this to the variogramST function? variogramST (in package gstat) assumes that the time gap between observations is constant. If you have approximately every half year observations, are some of them only a few days apart? Did you see a warning printed? If the time differences are very un-even, the whole activity may be pretty meaningless (with current implementation), and a mapping to stricter regularity might help. We have coding Friday tomorrow, drop by or send something useful and we might be able to work it out. -- Edzer Pebesma Institute for Geoinformatics (ifgi), University of Münster Heisenbergstraße 2, 48149 Münster, Germany. Phone: +49 251 83 33081 http://ifgi.uni-muenster.de GPG key ID 0xAC227795 signature.asc Description: OpenPGP digital signature ___ R-sig-Geo mailing list R-sig-Geo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo
Re: [R-sig-Geo] Spacetime regression
On 13.02.2014 14:00, Edzer Pebesma wrote: On 02/13/2014 01:30 PM, Roelof Coster wrote: When I make the sample space-time variogram (with variogramST), it automatically chooses a time-lag difference of about 2 days. This is much too small to be meaningful for my data; half-year periods would be interesting. Is there a way to tell this to the variogramST function? variogramST (in package gstat) assumes that the time gap between observations is constant. If you have approximately every half year observations, are some of them only a few days apart? Did you see a warning printed? If the time differences are very un-even, the whole activity may be pretty meaningless (with current implementation), and a mapping to stricter regularity might help. We have coding Friday tomorrow, drop by or send something useful and we might be able to work it out. A quick work around along Edzer's suggestion could be the following: Currently, variogramST calculates the empirical variogram per temporal lag tlag for pairs of spatial slices such as (STFDF[,i], STFDF[,i+tlag]) while tlag is from a vector like tlags=0:5. Given your data has been collected within a couple of days every half year and encoded as such, you might want to use fake dates that set all these entries to the same point in time, i.e. the same temporal index. This way, STFDF[,i] and STFDF[,i+1] would return two time slices half a year (in fake dates) apart from each other and that would be the temporal width variorgamST would be using as well. Otherwise, lets say your data has continuously be recorded while a sensor moved across the Netherlands revisiting each point every half year, some more careful thinking would be needed. However, the usefulness of spatio-temporal kriging depends on the spatio-temporal properties of the process you are looking at (i.e. will there be any explanatory value between observations separated half a year). HTH, Ben ___ R-sig-Geo mailing list R-sig-Geo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo -- Benedikt Gräler ifgi - Institute for Geoinformatics University of Muenster http://ifgi.uni-muenster.de/graeler Phone: +49 251 83-33082 Mail: ben.grae...@uni-muenster.de signature.asc Description: OpenPGP digital signature ___ R-sig-Geo mailing list R-sig-Geo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo
Re: [R-sig-Geo] Spacetime regression
when confronted with a large dataset i usually begin by trying methods out on subsets, e.g. start with 2^n for n = 8 and work your way up to 2^17... you might find convergence to the answer to your questions before analyzing the full dataset. Lee De Cola - Original Message - From: Roelof Coster roelofcos...@gmail.com To: r-sig-geo@r-project.org Sent: Thursday, February 13, 2014 7:30:04 AM Subject: [R-sig-Geo] Spacetime regression Hi all, I want to do a spatio-temporal regression on a quite large dataset. I have 100 k records. These correspond to measurements taken at 3000 locations, approximately every half year. The geographic area is all of the Netherlands (240 x 300 km). Is spatio-temporal kriging advisable for a dataset that is so large? When I make the sample space-time variogram (with variogramST), it automatically chooses a time-lag difference of about 2 days. This is much too small to be meaningful for my data; half-year periods would be interesting. Is there a way to tell this to the variogramST function? Thanks in advance, Roelof Coster [[alternative HTML version deleted]] ___ R-sig-Geo mailing list R-sig-Geo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo [[alternative HTML version deleted]] ___ R-sig-Geo mailing list R-sig-Geo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo
Re: [R-sig-Geo] Spacetime regression
Thanks for the answers. I have cleaned up the data by rounding the dates to half years, and now the variogram turns out beautiful. Now I can proceed to kriging and see what I get. Best regards, Roelof Coster 2014-02-13 17:54 GMT+01:00 ldec...@comcast.net: when confronted with a large dataset i usually begin by trying methods out on subsets, e.g. start with 2^n for n = 8 and work your way up to 2^17... you might find convergence to the answer to your questions before analyzing the full dataset. Lee De Cola -- *From: *Roelof Coster roelofcos...@gmail.com *To: *r-sig-geo@r-project.org *Sent: *Thursday, February 13, 2014 7:30:04 AM *Subject: *[R-sig-Geo] Spacetime regression Hi all, I want to do a spatio-temporal regression on a quite large dataset. I have 100 k records. These correspond to measurements taken at 3000 locations, approximately every half year. The geographic area is all of the Netherlands (240 x 300 km). Is spatio-temporal kriging advisable for a dataset that is so large? When I make the sample space-time variogram (with variogramST), it automatically chooses a time-lag difference of about 2 days. This is much too small to be meaningful for my data; half-year periods would be interesting. Is there a way to tell this to the variogramST function? Thanks in advance, Roelof Coster [[alternative HTML version deleted]] ___ R-sig-Geo mailing list R-sig-Geo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo [[alternative HTML version deleted]] ___ R-sig-Geo mailing list R-sig-Geo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo
