I got a .tif dataset with land cover classifications (so categorical values) which I want to replace with another value (integers) and export these values into a .txt-file following the ASCII format (this is required by the model I want to use the output for).
1. Is there any opportunity to export the actual values of the SpatRaster?
2. And are there any concerns about exporting to a .txt-file by defining the filename?
I was able to replace the values by using subst(), but when trying to export I was only able to produce output containing the ID.
r <- rast(nrows=3, ncols=3)
values(r) <- sample(3, ncell(r), replace=TRUE)
cls <- data.frame(id=1:3, cover=c("forest", "water", "urban"))
levels(r) <- cls
replacement <- c(10,20,30)
r_replaced <- subst(r,levels(r)[[1]]$cover, replacement)
writeRaster(r_replaced, "test.txt", filetype = "AAIGrid")
The output looks like this
ncols 3
nrows 3
xllcorner -180.000000000000
yllcorner -90.000000000000
dx 120.000000000000
dy 60.000000000000
NODATA_value 255
6 4 6
4 4 4
4 5 4
but I actually want it to look like this
ncols 3
nrows 3
xllcorner -180.000000000000
yllcorner -90.000000000000
dx 120.000000000000
dy 60.000000000000
NODATA_value 255
30 10 30
10 10 10
10 20 10
You can do this (note raw=TRUE)
# levels(r)[[1]][,1] == 1:3
r_replaced <- subst(r, c(1:3), c(10,20,30), raw=TRUE)
writeRaster(r_replaced, "test.asc", NAflag=-999, overwrite=T)
Result
readLines("test.asc", 10)
# [1] "ncols 3"
# [2] "nrows 3"
# [3] "xllcorner -180.000000000000"
# [4] "yllcorner -90.000000000000"
# [5] "dx 120.000000000000"
# [6] "dy 60.000000000000"
# [7] "NODATA_value -999"
# [8] " 10.0 30 20"
# [9] " 10 10 30"
#[10] " 10 30 30"
The problem with your approach is that r_replaced is still a categorical raster (see levels(r_replaced) for your code). You can also start out by removing the categories
levels(r) <- NULL
Although, with this example, you could also do
rr <- r * 10
writeRaster(rr, "test.asc", NAflag=-99, overwrite=TRUE)