Re: [netcdfgroup] easiest way to add an attribute to a variable in a netCDF file?

• To: "Lynnes, Christopher S. (GSFC-6102)" <christopher.s.lynnes@xxxxxxxx>
• Subject: Re: [netcdfgroup] easiest way to add an attribute to a variable in a netCDF file?
• From: Erik Noble <nobleeu@xxxxxxxxx>
• Date: Sat, 13 Aug 2011 14:12:19 -0400

Maybe someone has already mentioned NCL?
http://www.ncl.ucar.edu/Applications/

Basically you just extract the variable and tell it what the fill value should 
be. Then you can use the "where" command to make more _FillValues where they 
are needed.

a = addfile("netcdffile.nc","r")
x=a->variable                           ; 3D Variable
x!0 = "Time"
x!1 = "lat"
x!2 = "lon"
 .
 .
 .
x@_FillValue = -9999

  Assume you have a multi-dimensional numeric array x with a missing value 
(x@_FillValue). Use where to take the square root of x only at locations where 
x is positive, and set it to a missing value otherwise:

   xsqrt = where(x.gt.0,sqrt(x),x@_FillValue)
http://www.ncl.ucar.edu/Document/Functions/Built-in/where.shtml



Erik Noble
Center for Climate Systems Research, Columbia University
NASA Goddard Institute for Space Studies
2880 Broadway, New York, NY-10025, USA

Tel: +1 (212) 678-5512; Fax: +1 (212) 678-5552
E-mail: enoble@xxxxxxxxxxxxx, en2192@xxxxxxxxxxxx
WEB:  http://www.giss.nasa.gov/staff/enoble.html
GISS: http://www.giss.nasa.gov
CCSR: http://www.ccsr.columbia.edu
_______________________________________________________

On Aug 12, 2011, at 2:01 PM, Lynnes, Christopher S. (GSFC-6102) wrote:

> I have a netCDF file which is missing its _FillValue attributes.  I know what 
> they are supposed to be, so is there a utility that will let me add them, or 
> do I need to write a piece of code to do it?  Something like ncrename, but 
> where I can add attribute and value if not there?
> --
> Dr. Christopher Lynnes     NASA/GSFC, Code 610.2    phone: 301-614-5185
> 
> 
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• References:
  • [netcdfgroup] easiest way to add an attribute to a variable in a netCDF file?
    • From: Lynnes, Christopher S. (GSFC-6102)