R语言：Krig.check.xYx，Y，Z，weights，na.rm，verbose = verbose错误：x矩阵中不存在

如何解决R语言：Krig.check.xYx，Y，Z，weights，na.rm，verbose = verbose错误：x矩阵中不存在

我试图重现“ raster”包中提供的“ interpolation”命令中给出的以下示例。

library(fields)
library(raster)
## Not run: 
## Thin plate spline interpolation with x and y only
# some example data
r <- raster(system.file("external/test.grd",package="raster"))
ra <- aggregate(r,10)
xy <- data.frame(xyFromCell(ra,1:ncell(ra)))
v <- getValues(ra)

#### Thin plate spline model
library(fields) 
tps <- Tps(xy,v)
p <- raster(r)

# use model to predict values at all locations
p <- interpolate(p,tps)
p <- mask(p,r)

plot(p)
## change the fun from predict to fields::predictSE to get the TPS standard error
se <- interpolate(p,tps,fun=predictSE)
se <- mask(se,r)
plot(se)

## another variable; let's call it elevation
elevation <- (init(r,'x') * init(r,'y')) / 100000000
names(elevation) <- 'elev'
elevation <- mask(elevation,r)

z <- extract(elevation,xy)

# add as another independent variable
xyz <- cbind(xy,z)
tps2 <- Tps(xyz,v)
p2 <- interpolate(elevation,tps2,xyOnly=FALSE)

但是，出现以下错误：

Error in Krig.check.xY(x,Y,Z,weights,na.rm,verbose = verbose) : 
   NA's in x matrix

我正在以下条件下跑步： R版本3.6.1（2019-07-05） 平台：x86_64-w64-mingw32 / x64（64位） 运行于：Windows 10 x64（内部版本17763）

有什么想法要解决吗？