Re: Manipulating netCDF files

• To: "Waylon.Collins" <Waylon.Collins@xxxxxxxx>
• Subject: Re: Manipulating netCDF files
• From: "David Pierce" <dpierce@xxxxxxxx>
• Date: Fri, 11 Nov 2005 09:12:36 -0800 (PST)

As someone else already suggested, a scripting approach would take care of
this straightforwardly although it's probably not what you were
envisioning.

For example, the popular data analysis program R has a package "ncdf" that
could be used to make a script along these lines:

contents of fixvals.R:
----------------------

# Get command line args: input file name, varname, old val, new val
infile  <- commandArgs()[3]
varname <- commandArgs()[4]
oldval  <- commandArgs()[5]
newval  <- commandArgs()[6]

# open file, get data
ncid <- open.ncdf( infile, write=TRUE )
data <- get.var.ncdf( ncid, varname )
data[ data==oldval ] <- newval

# write out data
put.var.ncdf( ncid, varname, data )
close.ncdf( ncid )
------------------------

And then it could be run from the command line like this:

R --no-save filename.nc varname 32 45 < fixvals.R


Regards,

--Dave


Waylon.Collins wrote:
> Dear group members,
>
> After reviewed the Unidata list of software that manipulates netCDF
files, I have yet to find one that can perform the following task -- I
need command-line software (that can run in a Redhat Enterprise Linux
environment) that will allow me to replace data values, associated with
a particular variable, with values that I can specify. It needs to allow
for a logical operation. For example, the software needs to be able to
perform the following -- "Any datum of variable X, within netCDF file
with filename F.nc, that equals 32, change it to the value 45. Thus, the
original file F.nc is now altered, or the altered file is now named
G.nc". Any help will be greatly appreciated.
>
> Sincerely,
>
> Waylon
>
> --
> ********************************************************************** *
Waylon G. Collins                  Voice: (361)289-0959            * *
NOAA/National Weather Service      E-Mail: Waylon.Collins@xxxxxxxx * *
300 Pinson Drive                                                   * *
Corpus Christi, TX 78406                                           * *
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>
>


---------------------------------------------------------------
David W. Pierce        / Climate Research Division
Scripps Inst. Oceanog. / (858) 534-8276 (voice)
dpierce@xxxxxxxx       / (858) 534-8561 (fax)
---------------------------------------------------------------

• References:
  • Manipulating netCDF files
    • From: Waylon.Collins