[netCDF #XID-711290]: How to joins together netCDF files???

Hi Alessandro,

Thanks for telling me about IOIPSL, I had not heard about that.  If it already 
has a solution, it might be easiest to try to solve the problem with IOIPSL and 
get that to work.  For that, you would have to send us more details and maybe 
some test data, and it might take us some weeks to figure out the problem with 
someone else's software.

Another possibility is to use the freely available NCO (netCDF operators) 
package, briefly described here:

  http://www.unidata.ucar.edu/software/netcdf/software.html#NCO

From the NCO Users' Guide, there is a description of using the "ncpdq" program 
to do something like what you need:

ncpdq makes it possible to concatenate files along any dimension, not just the 
record dimension. First, use ncpdq to convert the dimension to be concatenated 
(i.e., extended with data from other files) into the record dimension. Second, 
use ncrcat to concatenate these files. Finally, if desirable, use ncpdq to 
revert to the original dimensionality. As a concrete example, say that files 
x_01.nc, x_02.nc, ... x_10.nc contain time-evolving datasets from spatially 
adjacent regions. The time and spatial coordinates are time and x, 
respectively. Initially the record dimension is time. Our goal is to create a 
single file that contains joins all the spatially adjacent regions into one 
single time-evolving dataset.

     for idx in 01 02 03 04 05 06 07 08 09 10; do # Bourne Shell
       ncpdq -a x,time x_${idx}.nc foo_${idx}.nc # Make x record dimension
     done
     ncrcat foo_??.nc out.nc       # Concatenate along x
     ncpdq -a time,x out.nc out.nc # Revert to time as record dimension

---------------------------------

Another possibility is to write a small program in C, Fortran, C++, or Java or 
perhaps in a scripting language such as perl, python, or ruby, that reads in 
the data fields and stitches them together one longitude at a time, writing the 
merged result fields to the output file.  Depending on programming skills, this 
might only take a day or two.

The psuedocode would be something like

open the 4 files
create an empty output file, fileout, with all the desired variables

for each variable
  for each longitude
     read slice1 from file1
     read slice2 from file2
     read slice3 from file3
     read slice4 from file4
     merge slices 1 through 4 into slice_global
     write out slice_global to fileout
  end for
end for

You could even create the output file using the "ncgen" tool, so you wouldn't 
have to write a program for that.

--Russ




Russ Rew                                         UCAR Unidata Program
address@hidden                     http://www.unidata.ucar.edu



Ticket Details
===================
Ticket ID: XID-711290
Department: Support netCDF
Priority: Normal
Status: Closed