R help - Feb 2017 - R version 3.3.2, Windows 10 -- gstat.predict() function often return NaN values (GSTAT Package)

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I am adding my message in the mail body as I found it missing from the mail that
finally got posted on the list.

I am trying to simulate a combination of two different random fields (yy1 and
yy2 different mean and correlation length) with an irregular boundary. I have
attached the picture of my expected outcome. The code is not giving such output
consistently and I am frequently getting atleast one of the yy1 and yy2 as as
NaN, which results in the Undesired output as shown in image.

The key steps I used are:

1)	Created two gsat objects with different means and psill (rf1 and rf2)
2)	Created two computational grids (one for each random field) in the form of
data frame with two variables "x" and "y" coordinates.
3)	Predicted two random fields using unconditional simulation. 

The code is fairly small hence I am pasting in here itself. Any help in this
regard would be highly appreciated.

## Code starts
==================================================================================library(gstat)

xy <- expand.grid(1:150, 1:200) # grid is created in the form of a dataframe
with x and y vectors
names(xy)<-c('x','y') # giving names to the variables

# Creating gsat objects

rf1<-gstat(formula=z~1,locations=~x+y,dummy = T,beta=c(1,0,0),
model=vgm(psill=0.025, range=5, model='Exp'), nmax=20)  # dummy=T treats
this as a unditional simulation
rf2<-gstat(formula=z~1,locations=~x+y,dummy = T,beta=c(4,0,0),
model=vgm(psill=0.025, range=10, model='Exp'), nmax=20)  # dummy=T
treats this as a unditional simulation

# Splitting the computational grid into two

rows<-nrow(xy)
xy_shift <- expand.grid(60:90, 75:100)
names(xy_shift)<-c('x','y')

library(dplyr) # for antijoin
xy1<-xy[1:(rows/2),]
xy1<-anti_join(xy1, xy_shift, by = c("x","y")) # creating
the irregular boundary
xy2<-rbind(xy[(rows/2+1):rows,],xy_shift)

# Simulation

yy1<- predict(rf1, newdata=xy1, nsim=1) # random field 1
yy2<- predict(rf2, newdata=xy2, nsim=1) # random field 2

yy<-rbind(yy1,yy2)

# Plotting the field

library(sp)
gridded(yy) = ~x+y
spplot(obj=yy[1])

## Code ends====================================================================
-----Original Message-----
From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Rathore,
Saubhagya Singh
Sent: Wednesday, February 15, 2017 12:37 PM
To: r-help at r-project.org
Subject: [R] R version 3.3.2, Windows 10 -- gstat.predict() function often
return NaN values (GSTAT Package)

______________________________________________
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and provide commented, minimal, self-contained, reproducible code.
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