You don't describe your problem completely, and you also do not provide a reproducible example, so I can only make a wild guess: your z variable takes an extreme value at the prediction location(s) where you see the high predictions.
On 12/04/2014 08:19 AM, Bingwei Tian wrote: > Dear list, > > I am doing a 3D estimation of logtransfered subsurface temperature (with a > strong vertical trend) with a Nested 3D variogram, but the results show very > high value over than origin data. > This is not normal and absolutely wrong if I back transfer logged data. > > I attached the > <http://r-sig-geo.2731867.n2.nabble.com/file/n7587514/vgm.png> and anyone > who knows what is the reason for the very high value differ from origin > data? > Or what kind of processing I should to do for the data back transfer? Thanks > in advance for any help. > > Data: > summary((spdf$logt)) > Min. 1st Qu. Median Mean 3rd Qu. > 0.741937344729 3.487375077900 3.908014984030 3.952886346280 4.452019006490 > Max. > 5.733988316710 > > Model: Nested 3D varigram > uk.eye1 <- vgm(psill = 0.155, model = "Gau", range=700, nugget=0) > uk.eye <- vgm(psill = 0.125, model = "Sph", range=35000, nugget=0, > add.to=uk.eye1) > model psill range > 1 Nug 0.000 0 > 2 Gau 0.155 700 > 3 Nug 0.000 0 > 4 Sph 0.125 35000 > UK: > logt.uk <- krige(log(t)~z, spdf, grid, model = uk.eye, nmax = 20) > > Result: > > summary((logt.uk$var1.pred)) > Min. 1st Qu. Median Mean 3rd Qu. > -1.66562650678 3.30346488250 3.76836777085 3.81376070431 4.24457939254 > Max. > 15.05945622140 > > > > ----- > Bingwei > > Ph.D. Student > Kyoto University > C-1-2-225, Katsura Campus, Kyoto University, > Nishikyo-ku, 〒615-8530, Kyoto, Japan > -- > View this message in context: > http://r-sig-geo.2731867.n2.nabble.com/What-is-the-reason-for-Very-high-value-by-Universal-Kriging-based-on-Nested-3D-varigram-tp7587514.html > Sent from the R-sig-geo mailing list archive at Nabble.com. > > _______________________________________________ > R-sig-Geo mailing list > R-sig-Geo@r-project.org > https://stat.ethz.ch/mailman/listinfo/r-sig-geo > -- Edzer Pebesma, Co-Editor-in-Chief Computers & Geosciences 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
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