This is perfect! Thank you! ________________________________________ From: r-sig-geo-boun...@r-project.org [r-sig-geo-boun...@r-project.org] on behalf of Edzer Pebesma [edzer.pebe...@uni-muenster.de] Sent: Sunday, November 24, 2013 12:39 PM To: r-sig-geo@r-project.org Subject: Re: [R-sig-Geo] back with cutoff/variogram question
Erin, it is in https://r-forge.r-project.org/scm/viewvc.php/pkg/src/sem.c?view=markup&root=gstat file sem.c, line 692 defaults.h defines: #define DEF_fraction 0.33333 /* fraction of max_dist for def. cutoff */ which is the default value for gl_fraction. The default number of lag classes is 15 (gl_n_intervals). You can change these defaults to e.g. 0.5 and 25 by: variogram(gstat(NULL, "zinc", zinc~1, meuse, set=list(fraction=.5,intervals=25))) On 11/24/2013 04:53 PM, Hodgess, Erin wrote: > Hi! > > This is from the gstat variogram. > > I tried to track this down via the vario.c function, but I'm having some > trouble with it. > > ________________________________________ > From: b.rowling...@gmail.com [b.rowling...@gmail.com] on behalf of Barry > Rowlingson [b.rowling...@lancaster.ac.uk] > Sent: Sunday, November 24, 2013 3:08 AM > To: Hodgess, Erin > Cc: r-sig-geo@r-project.org > Subject: Re: [R-sig-Geo] back with cutoff/variogram question > > On Sun, Nov 24, 2013 at 5:46 AM, Hodgess, Erin <hodge...@uhd.edu> wrote: >> Hello again. >> >> I'm back with the variogram question. Here is the info from the help file: >> >> cutoff: spatial separation distance up to which point pairs are >> included in semivariance estimates; as a default, the length >> of the diagonal of the box spanning the data is divided by >> three. >> >> By the box spanning the data, does that mean the bounding box, please? If >> so, wouldn't that just be 2, please? > > There's quite a few 'variogram' functions in various R packages so it > might help if you told us which one! > > I should think that "the box spanning the data" is indeed the > bounding box. I don't see what you think would be '2' in this case > though, unless the diagonal length of the bounding box happened to be > 6. > > For data that included points at (0,0) and (1,1) the diagonal would > have length sqrt(2) and so the cutoff default should be sqrt(2)/3. > Note you have to actually have points at those coordinates and not > just generate 1000 random points in the unit square. > > A few simple experiments with simulated point data sets with various > bounding boxes should confirm this, or you could just look at the > code? > > Barry > > _______________________________________________ > R-sig-Geo mailing list > R-sig-Geo@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. Phone: +49 251 83 33081 http://ifgi.uni-muenster.de GPG key ID 0xAC227795 _______________________________________________ R-sig-Geo mailing list R-sig-Geo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo