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Fig. 5.8: Variogram for original variable, and regression residuals.... # fit a variogram (original variable): zinc.svar <- variogram(log1p(zinc)~1, meuse) plot(zinc.svar) # initial variogram: zinc.ivgm <- vgm(nugget=0, model="Exp", range=sqrt(diff(meuse@bbox["x",])^2 + diff(meuse@bbox["y",])^2)/4, psill=var(log1p(meuse$zinc))) zinc.vgm <- fit.variogram(zinc.svar, model=zinc.ivgm) zinc.vgm zinc.vgm.plt <- plot(zinc.svar, zinc.vgm, pch="+", pl=TRUE, col="black", main="log1p(zinc)") # residuals: zinc.rsvar <- variogram(residuals(step.zinc)~1, meuse.ov) zinc.ivgm <- vgm(nugget=0, model="Exp", range=sqrt(diff(meuse@bbox["x",])^2 + diff(meuse@bbox["y",])^2)/4, psill=var(residuals(step.zinc))) zinc.rvgm <- fit.variogram(zinc.rsvar, model=zinc.ivgm) zinc.rvgm zinc.rvgm.plt <- plot(zinc.rsvar, zinc.rvgm, pc="+", pl=FALSE, col="black", main="Residuals") # synchronize the two plots: zinc.rvgm.plt$x.limits <- zinc.vgm.plt$x.limits zinc.rvgm.plt$y.limits <- zinc.vgm.plt$y.limits print(zinc.vgm.plt, split=c(1,1,2,1), more=TRUE) print(zinc.rvgm.plt, split=c(2,1,2,1), more=FALSE) dev.off() |
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