Re: [netcdf-java] Your netcdf question.

• To: "Steve Loch" <sgl@xxxxxxxxxx>
• Subject: Re: [netcdf-java] Your netcdf question.
• From: "Rich Signell" <rsignell@xxxxxxxx>
• Date: Mon, 8 Dec 2008 08:38:11 -0500

Matlab/NetCDF users,

Please be aware that there are many different toolkits for accessing
NetCDF files from Matlab.

Some use mex files, some use NetCDF-Java.
Some automatically scale using "scale_factor" and "add_offset", some don't.

In Chuck Denham's tookbox (which uses a mex file, not NetCDF-Java),
there are global variables that can override the default behavior.
If you don't set the variables, the default behavior is to NOT
autoscale, but in my startup.m file, I have:

global nctbx_options
nctbx_options.theAutoNaN=1;
nctbx_options.theAutoscale=1;

which changes the default behavior to autoscale.

I just wanted to mention this because I've seen Matlab users who used
someone elses startup.m file as a template sometimes unaware of this
issue, which can lead to confusion.

Thanks,
Rich

On Mon, Dec 8, 2008 at 4:12 AM, Steve Loch <sgl@xxxxxxxxxx> wrote:
> Kevin,
>
> The following is what I've dug out of Chuck Denham's toolbox that we have 
> used here in BODC for many years. Namely
>
> result = result .* theScalefactor + theAddoffset;
>
> in retrieving the data from a variable. If the variable doesn't have the 
> attribute scale_factor then it will be taken as 1. Similar sentiments apply 
> to theAddoffset
> which will be zero unless given explicitly. If you use the toolbox it'll do 
> it for you with the auto-scaling option (help netcdf reveals all!)
>
> Steve Loch
> BODC
>
>
>
>
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-- 
Dr. Richard P. Signell   (508) 457-2229
USGS, 384 Woods Hole Rd.
Woods Hole, MA 02543-1598

• References:
  • [netcdf-java] Your netcdf question.
    • From: Steve Loch