Trouble overlaying plots in R

Question

I've produced a raster using IDW to make predictions across California, and now I'm trying to overlay the raster image with the border/shapefile of California.

I've ensured the CRS projections are the same for both plots, however I still can't get both to show up.

The following is the code for how I produced the raster:

x.range <- as.double(range(zip_table@coords[,1]))
y.range <- as.double(range(zip_table@coords[,2]))

grd <- expand.grid(x=seq(from=x.range[1], to=x.range[2], by=0.01),
                   y=seq(from=y.range[1], to=y.range[2], by=0.01))

## convert grid to SpatialPixel class
coordinates(grd) <- ~ x + y
gridded(grd) <- TRUE

idw1 <- gstat::idw(TELERATIO ~ 1, zip_table, grd, idp = 2) 

idw.output <- as.data.frame(idw1)
names(idw.output)[1:3] <- c("lng","lat","var1.pred")

r <- raster(idw1)```

And the CA state file I downloaded using a work around of the raster::getData function:

CA <- gadm36_USA_1_sp[gadm36_USA_1_sp$NAME_1 =='California',]

When I produce my plots, only the raster shows up:

plot(CA, add = TRUE)

Answer 1

California is not at latitude -120, unless there's been an earthquake and its drifted off into the Pacific (although +30 longitude probably puts it in the South Atlantic...). It seems that latitude and longitude have been transposed.

Going through your code from the first line with a known-good lat-long data set results in a lat-long-correct raster output, so I think your zip_table object has its coordinates transposed already.