[netcdf-java] Writing unsigned data to attributes

• To: netcdf-java@xxxxxxxxxxxxxxxx
• Subject: [netcdf-java] Writing unsigned data to attributes
• From: Alex Fraser <adfries@xxxxxxxx>
• Date: Mon, 17 Jun 2013 12:05:31 +1000 (EST)

Hello,

I'm trying to write unsigned data to attributes, but I can't quite get it 
working. I've seen the mailing list threads on reading from unsigned 
attributes, but I haven't seen much discussion about writing.

Suppose I have an unsigned byte variable, and I want to set its `valid_range` 
attribute. I tried using `Array.setUnsigned`, but the values are still written 
as signed. In this case the valid range is 0..255, which comes out as 0..-1. 
This causes ToolsUI to read the variable as being empty.

I would just use shorts instead of bytes, but this approach does not seem to be 
reliable for all attributes: it fails for the `_FillValue` attribute which the 
nc4 IOSP says must be the same type as the variable.

I asked a question on StackOverflow; it has some simplified code in it:

    
http://stackoverflow.com/questions/17139391/netcdf-java-how-to-write-unsigned-attribute

Versions:
 - NetCDF-Java 4.3.16
 - libnetcdf 4.2.1
 - ToolsUI 4.3

Let me know if you need more information.

Cheers,
Alex

-- 
Alex Fraser
Software Engineer
VPAC Ltd.

• Follow-Ups:
  • Re: [netcdf-java] Writing unsigned data to attributes
    • From: John Caron