Dear there,
I tried to compare idw and gstat in library(gstat). I specified idp as 0.5 in
both functions, I expected identical results, but what I got are different as
shown for the first five samples. Please help. Thanks.
> data(meuse)
> coordinates(meuse) = ~x+y
> data(meuse.grid)
> gridded(meuse.grid) = ~x+y
> x <- idw(zinc~1, meuse, meuse.grid, idp=0.5)
[inverse distance weighted interpolation]
> as.data.frame(x)[1:5,]
var1.pred var1.var x y
1 482.8753 NA 181180 333740
2 487.0065 NA 181140 333700
3 483.9747 NA 181180 333700
4 481.2115 NA 181220 333700
5 494.8720 NA 181100 333660
> data(meuse)
> data(meuse.grid)
> meuse.gstat <- gstat(id = "zinc", formula = zinc ~ 1, locations = ~ x + y,
+ data = meuse, nmax = 7, set = list(idp = .5))
> meuse.gstat
data:
zinc : formula = zinc`~`1 ; data dim = 155 x 12 nmax = 7
set idp = 0.5;
~x + y
> z <- predict(meuse.gstat, meuse.grid)
[inverse distance weighted interpolation]
> z[1:5,]
x y zinc.pred zinc.var
1 181180 333740 626.3628 NA
2 181140 333700 645.9319 NA
3 181180 333700 629.7041 NA
4 181220 333700 615.1368 NA
5 181100 333660 682.3401 NA
Cheers,
Jin
--------------------------------------------
Jin Li, PhD
Spatial Modeller/
Computational Statistician
Marine & Coastal Environment
Geoscience Australia
Ph: 61 (02) 6249 9899
Fax: 61 (02) 6249 9956
email: [EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>
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