How can I edit the _FillValue attribute in a NetCDF file.

When editing NetCDF files, ncwriteatt works for editing any attribute except for the _FillValue attribute. So how can I change the value of the _FillValue attribute in NetCDF files that have already been created?

Answer 1

[Guillaume Galibert]

You will need to create a new variable with this new _FillValue, read the data from the original variable, update any value with FillValue with the new FillValue, store this data in your new variable and then you can delete the original variable.

[munsense]

Thanks

[Walter Roberson]

It seems to me that the actual fill value is stored in the data, so changing it requires that something scan the data and assign new values to the locations that currently have the fill value. netCDF files do not have a table of which values are valid or not with the fill value being substituted for the invalid values when the data is read: they just store the data handed to them and it is up to the program to compare the data read back to the fillvalue to determine which locations were valid.