[netcdf-java] Writing data for a single timestep

[John Caron]

Hi Christopher:

You are right that writing data a record at a time is the key to efficiently writing files with an unlimited dimension. Note that in this case you need:

        Dimension timeDim = outNc.addUnlimitedDimension(this.TIME);

Ive just added an example at:

  http://www.unidata.ucar.edu/software/netcdf-java/tutorial/NetcdfWriteable.html#RecordAtaTime

Let me know if that helps, and if you have more questions.

John

Christopher Mueller wrote:
> Hi all,
> 
> I’ve successfully created an empty NetcdfFile but I’m having some 
> difficulty writing data to the file.  Just for a bit of context, I’m 
> trying to write data from a list of particles – each of which has an id, 
> lat, lon and concentration – to the nc file one timestep at a time.
> 
> In other words, I have a loop where a new list of particles is generated 
> each cycle.  After they are generated, they need to be written to the nc 
> file as a “new” timestep.
> 
> Basically, I’d like to have a method that accepts the list of particles 
> (which contain lat, lon, conc) and a time and simply write a new time 
> record with all of the particles in the list.  Is that possible??
> 
> I’m completely lost as to how I can do this efficiently.  All of the 
> examples I can find show writing all of the variables for all times at 
> once – which doesn’t help (too much data to hold in memory until the end).
> 
> Any help is very much appreciated.
> 
> Thanks,
> Chris
> 
> Here’s my file creation code just in case there’s something wrong here...:
> 
>         outNc = NetcdfFileWriteable.createNew(fileLoc, true);
>         
>         //make the dimensions
>         Dimension timeDim = outNc.addDimension(this.TIME, timeSteps);
>         Dimension partDim = outNc.addDimension(this.PARTICLE, numParts);
>         
>         ArrayList dims = new ArrayList();
>         
>         //add coordinate variables
>         outNc.addVariable(this.TIME, DataType.INT, new 
> Dimension[]{timeDim});
>         outNc.addVariable(this.PARTICLE, DataType.INT, new 
> Dimension[]{partDim});
>         
>         dims.add(timeDim);
>         dims.add(partDim);
>         
>         //add the variables
>         outNc.addVariable(this.LAT, DataType.DOUBLE, dims);
>         outNc.addVariable(this.LON, DataType.DOUBLE, dims);
>         outNc.addVariable(this.CCONC, DataType.DOUBLE, dims);
>         
>         //add attributes to the variables
>         outNc.addVariableAttribute(this.LAT, "units", "deg North");
>         outNc.addVariableAttribute(this.LON, "units", "deg East");
>         outNc.addVariableAttribute(this.CCONC, "units", "moles liter^-1");
>         
>         try {
>             outNc.create();
>         } catch (IOException ex) {
>             ex.printStackTrace();
>         }
> 
> 
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