Exporting String to NetCDF

Question

I've already read a Q&A stating that because NetCDF does not support primitive string type variables, that it is impossible to export a string to a NetCDF file.

For example:

testvalsnodvar = {"VOL_FRACTION01"}; Export["W:\\LPF_extractor\\test.nc", {"vals_nod_var" ->testvalsnodvar}, "Datasets"]

gives a Java error stating that this is an incorrect format for Datasets. Is there a way around this or am I stuck?

Answer 1

Convert the string to a list of integers using ToCharacterCode, and then convert back using FromCharacterCode.

testvalsnodvar = {"VOL_FRACTION01"};
Export["test.nc", {"vals_nod_var" -> 
   ToCharacterCode@testvalsnodvar}, "NetCDF"]
(* "test.nc" *)

Import[
  "test.nc", {"Datasets", "vals_nod_var"}] // FromCharacterCode
(* {"VOL_FRACTION01"} *)

Answer 2

No need for workarounds in WL 13.1+:

In[1]:= Export["test.nc", "vals_nod_var" -> {"VOL_FRACTION01"}]

Out[1]= "test.nc"

In[2]:= Import["test.nc", "vals_nod_var"]

Out[2]= {"VOL_FRACTION01"}

By default, Export chooses netCDF-4 format for the file:

In[3]:= Import["test.nc", "Version"]

Out[3]= "NC4 Enhanced"

If you need to Export a string to the classic netCDF data model it will still work, but the string will be exported as an array of characters, thus adding one dimension:

In[4]:= Export["test.nc", "vals_nod_var" -> {"VOL_FRACTION01"}, "Version" -> "Classic"]

Out[4]= "test.nc"

In[5]:= Import["test.nc", "vals_nod_var"]

Out[5]= {{"V", "O", "L", "_", "F", "R", "A", "C", "T", "I", "O", "N", "0", "1"}}