Ciao Giovanni,
First of all I'd suggest updating to netCDF-JAVA 4.3 and use
NetcdfFileWriter or NetcdfCFWriter instead of NetcdfFileWriteable which
is now deprecated.
Changing the length of the dimensions don't actually change the shape of
the underlying array of data. To do that you need to subset the variable
and get a new variable from the original one.You can use the section
method for that purpose:
http://www.unidata.ucar.edu/software/netcdf-java/v4.3/javadoc/ucar/nc2/Variable.html#section(java.util.List)
<http://www.unidata.ucar.edu/software/netcdf-java/v4.3/javadoc/ucar/nc2/Variable.html#section%28java.util.List%29>
Also, if working with the variable objects in memory works for you and
you have valid CDM grids, you can simply make a GridDataset and then
subset the grids with the makeSubset method. That could be the code snippet:
NetcdfDataset ds = NetcdfDataset.openDataset(fileIn);
GridDataset gds = new GridDataset(ds);
GridDatatype uGrid = gds.findGridByName("u");
GridDatatype vGrid = gds.findGridByName("v");
Range zRange = new Range(0,0);
uGrid = uGrid.makeSubset(null, zRange, null, 1, 1, 1);
vGrid = vGrid.makeSubset(null, zRange, null, 1, 1, 1);
If you have to write out a file, I think this could work:
String fileOut ="out.nc";
NetcdfDataset ds = NetcdfDataset.openDataset(fileIn);
GridDataset gds = new GridDataset(ds);
List<String> wantedVars = new ArrayList<String>();
wantedVars.add("u");
wantedVars.add("v");
Range zRange = new Range(0,0);
NetcdfCFWriter writer = new NetcdfCFWriter();
writer.makeFile(fileOut, gds, wantedVars, gds.getBoundingBox(),
1, zRange, null, 1, false, NetcdfFileWriter.Version.netcdf3 );
Hope it helps.
On 03/13/2013 08:47 AM, Giovanni wrote:
Hi all,
I'm new to netCDF and I've a simple (I think) problem.
I've a netCDF file containing currents forecast (u and v variables)
for 3 days and 33 deep ocean levels. Now I would to remove all deep
levels but the first one (0.0 - surface level).
How I can do it?
I tryed this but does't works:
String fileIn = "C:/Users/Test/Desktop/latest.nc";
NetcdfFileWriteable aa =
NetcdfFileWriteable.openExisting(fileIn);
List<Variable> vars2 = aa.getVariables();
for (Variable va : vars2) {
System.out.println("Variable name :" + va.getFullName());
List<Dimension> dims = va.getDimensions();
for (Dimension di : dims) {
System.out.println("dim name: " + di.getName() + "
len:" + di.getLength());
if (di.getName().equals("Depth")) di.setLength(1);
}
}
aa.finish();
aa.finish();
aa.close();
This is my output:
Variable name :u
dim name: MT len:3
dim name: Depth len:33
dim name: Y len:30
dim name: X len:38
Variable name :MT
dim name: MT len:3
Variable name :Depth
dim name: Depth len:1
Variable name :Latitude
dim name: Y len:30
dim name: X len:38
Variable name :Longitude
dim name: Y len:30
dim name: X len:38
Variable name :v
dim name: MT len:3
dim name: Depth len:1
dim name: Y len:30
dim name: X len:38
What could be wrong?
Best regards
Giovanni
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