MATLAB Answers

Angela
0

Creating netCDF files: How can I set the order of the dimensions in a field?

Asked by Angela
on 18 Feb 2013
I have created a netCDF file with 3 dimensions (dim1,dim2,dim3) and a field that is defined on the (dim1,dim2,dim3) space. ncdump gives me
NetCDF-3 Classic myfile.nc {
dimensions:
dim1 = 12 ;
dim2 = 96 ;
dim3 = 14 ;
variables:
// Preference 'PRESERVE_FVD': false,
// dimensions consistent with ncBrowse, not with native MATLAB netcdf package.
single dim1(dim1), shape = [12]
single dim2(dim2), shape = [96]
int32 dim3(dim3), shape = [14]
single field(dim3,dim2,dim1), shape = [14 96 12]
How can I set the order of the dimensions on which the field is defined, i.e. so that ncdump will give me
single field(dim1,dim2,dim3), shape = [12 96 14]
? This is what I run for creating the file:
file='infile.nc';
dim2 = nc_varget ( file, 'dim2' );
dim3 = nc_varget ( file, 'dim3' );
field = nc_varget ( file, 'field' );
vardata_dim1 = [1 2 3 4 5 6 7 8 9 10 11 12];
vardata_dim2 = dim2;
vardata_dim3 = dim3;
vardata_field = field;
ncid = netcdf.create('myfile.nc','NC_WRITE');
dim_dim1 = netcdf.defDim(ncid,'dim1',12);
dim_dim2 = netcdf.defDim(ncid,'dim2',96);
dim_dim3 = netcdf.defDim(ncid,'dim3',14);
varID_dim1 = netcdf.defVar(ncid,'dim1','float',dim_dim1);
varID_dim2 = netcdf.defVar(ncid,'dim2','float',dim_dim2);
varID_dim3 = netcdf.defVar(ncid,'dim3','int',dim_dim3);
varID_field = netcdf.defVar(ncid,'field','float',[dim_dim1 dim_dim2 dim_dim3]);
netcdf.endDef(ncid);
netcdf.putVar(ncid,varID_dim1,vardata_dim1);
netcdf.putVar(ncid,varID_dim2,vardata_dim2);
netcdf.putVar(ncid,varID_dim3,vardata_dim3);
netcdf.putVar(ncid,varID_field,vardata_field);
netcdf.close(ncid)

  0 Comments

Sign in to comment.

1 Answer

Answer by Ashish Uthama on 19 Feb 2013
 Accepted Answer

%Account for moving from Column major to Row major ordering
colMajorDims = [dim_dim1 dim_dim2 dim_dim3];
rowMajorDims = fliplr(colMajorDims);
varID_field = netcdf.defVar(ncid,'field','float',rowMajorDims);
vardata_field = permute(vardata_field, [3 2 1]);
This post http://www.mathworks.com/matlabcentral/newsreader/view_thread/245539 explains the observed behavior in some detail. Please post back if any of that explanation is not clear.

  1 Comment

Works nicely, thanks a lot.

Sign in to comment.