QGIS reads blank cells as "nan" instead of "NULL"

Question

I use QGIS to visualise my data but I use R when I have to do many treatments on my attribute tables. (package terra)

But when I write vector data with R, the Na's appear in QGIS attribute table as "nan" when it usually writes "NULL" in grey when the cell is blank. The columns remain considered as real though "nan" values are present.

It is a problem since I can't select attributes by the expressions "field" is null or "field" = "nan".

I tried to replace them with if("field" = "nan", NULL, "field") without success either.

Do you know a way to change these "nan" to NULL? Preferably on the R side.

Answer 1

I wouldn't be able to help with sorting this in R, however regarding the post-processing in QGIS, you current request in the field calculator is:

if("field" = "nan", NULL, "field")

which you said doesn't work. I would suggest to try either of the two following syntaxes:

if("field" = 'nan', NULL, "field")

or

if("field" = 'nan', "", "field")

and see if you get any better results.