[R-sig-Geo] distances reported by gstat when cokriging

Tom Gottfried tom.gottfried at tum.de
Fri Mar 16 14:53:30 CET 2012


Dear list(en)ers,

I wonder what the "dist" is, which is in the output of predict.gstat() 
with debug.level=16. I expect it to be the distance between the 
coordinate pair given in the same line and the prediction location. I 
verified this for the coordinates and distances given for "data id: 0" 
in the below example (and its true), but for "data id: 1" it's always 
"dist: 0". Is there a way to get the distances for the second covariate? 
I see it's simple in the example, because data are colocated, but the 
problem arose in a case with non-colocated covariates.
Here's the example:

library(gstat)
data(meuse)
coordinates(meuse) <- ~x+y
variog <- variogram(zinc~1, meuse)
varmod <- fit.variogram(variog, vgm(150000, "Exp", 1000))
data(meuse.grid)
coordinates(meuse.grid) <- ~x+y
g <- gstat(NULL, "z", zinc~1, meuse, model=varmod, nmax=10)
g <- gstat(g, "dist", I(dist*1000)~1, meuse, nmax=10)
variog.g <- variogram(g)
g <- fit.lmc(variog.g, g, vgm(100000, "Exp", 500, 1000))
meuse.point <- meuse.grid[sample(1:nrow(meuse.grid), 1),]
predict(g, newdata=meuse.point, debug.level=16)

Thanks!
Tom

-- 
Technische Universität München
Department für Pflanzenwissenschaften
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Alte Akademie 12
85350 Freising / Germany
Phone: ++49 (0)8161 715324
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email: tom.gottfried at wzw.tum.de
http://www.wzw.tum.de/gruenland



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