I am trying to store several columns of the data, and then merge them with the other data when necessary. However, the data could only be merged with other data when I created it at the start, and it fails after fwrite and fread the data.


```
region <- climatebound_rast |> as.data.table(xy = TRUE)
fwrite(region, "region.csv")
region2 <- fread("region.csv", stringsAsFactors = TRUE)

all.equal(region,region2)
[1] TRUE


TEST <- raster_to_table[Variable=="npp"&Model=="DLEM", 1:4]

# 1. Merge raster data with region data
merged_region <- merge(TEST, region, all.x = TRUE) |> 
 drop_na(region) 

merged_region

Key: <x, y>
 x y Model Variable region
 <num> <num> <char> <char> <fctr>
 1: 87.99277 49.0312 DLEM npp MNG
 2: 88.49277 48.5312 DLEM npp MNG
 3: 88.49277 49.0312 DLEM npp MNG
 4: 88.99277 48.0312 DLEM npp MNG
 5: 88.99277 48.5312 DLEM npp MNG
 --- 
5846: 161.49277 68.5312 DLEM npp RUS
5847: 161.99277 68.5312 DLEM npp RUS
5848: 161.99277 69.0312 DLEM npp RUS
5849: 162.49277 68.5312 DLEM npp RUS
5850: 162.49277 69.0312 DLEM npp RUS

merged_region2 <- merge(TEST, region2, all.x = TRUE) |> 
 drop_na(region) 

merged_region2

Key: <x, y>
Empty data.table (0 rows and 5 cols): x,y,Model,Variable,region


```