[R-sig-Geo] question about simulating patchy landscapes

[Dylan Beaudette]

On Thursday 25 September 2008, Edzer Pebesma wrote:
> demo(uisim)

This seems work work with the demo code, but not with another example using my 
own data:

# setup
library(gstat)
library(spgrass6)

# load GRASS region settings
G <- gmeta6()
grd <- gmeta2grd()

# make a new grid from GRASS region
new_data <- SpatialGrid(grd)


# works fine:
var.model <- vgm(psill=10, model="Exp", range=1000)
sim <- predict(gstat(formula=z~1, dummy=TRUE, beta=0, model=var.model, 
nmax=20), newdata = new_data, nsim = 1)

# does not work -- produces a field of '0' values
sim <- predict(gstat(formula=z~1, dummy=TRUE, beta=0, model=var.model, 
nmax=20), newdata = new_data, nsim = 1, indicators=TRUE)


# any ideas on why UISIM works in the demo, and not in my examples? I have 
noticed that the syntax is slightly different in the demo, could this be the 
cause:

# prediction grid:
data(meuse.grid)
gridded(meuse.grid) = ~x+y

# define variable as dummy data
v = vgm(.25, "Sph", 900)
g = gstat(NULL, "var1", x~1, beta = .5, nmax = 20, model = v, dummy = TRUE)

# simulation of a single variable
out = predict(g, meuse.grid, nsim = 20, indicators = TRUE)

Thanks,
Dylan

-- 
Dylan Beaudette
Soil Resource Laboratory
http://casoilresource.lawr.ucdavis.edu/
University of California at Davis
530.754.7341