Create a grid for more than one country in R

Question

Some time ago I posted my own answer to create a grid inside a country to be used in kriging interpolation:

0........0.kriging error messages, grid file problem ? (automap, gstat)

This grid was for South Africa. Now I have data point for Lesotho (the hole inside SA), but cant get around it, to work with both together. I need a joint grid for kriging in gstat.

I used makegrid in sp:

SA0 <- raster::getData("GADM", country = "South Africa", level = 0)
plot(SA0)
SA0grd <- makegrid(SA0, n = 2000)
colnames(SALgrd) <- c('Longitude','Latitude')

SA0grd_pts <- SpatialPoints(coords = SALgrd, 
                    proj4string=CRS(proj4string(SA0)))



SALgrd_pts_in <- SALgrd_pts[SAL0, ]

plot(SALgrd_pts_in)

I tried this , did not worK

SAL0 <- raster::getData("GADM", country = c("South Africa", "Lesotho"), level = 0)

How can I create a grid for SA and Lesotho together?

Answer 1

It seems like you cannot pass multiple country arguments to raster::getData(), but you could simply merge two individual datasets using rbind():

library(sp)
library(raster)

SA0 <- raster::getData("GADM", country = "South Africa", level = 0)
les <- raster::getData("GADM", country = "Lesotho", level = 0)

sa_full <- rbind(SA0, les)

SA0grd <- sp::makegrid(sa_full, n = 2000)
colnames(SA0grd) <- c('Longitude','Latitude')

SA0grd_pts <- sp::SpatialPoints(coords = SA0grd, 
                                proj4string=CRS(proj4string(sa_full)))

SA0grd_pts_in <- SA0grd_pts[sa_full, ]

plot(SA0grd_pts_in)

^{Created on 2022-08-05 by the reprex package (v2.0.1)}