How to write a large matrix to a nc-file

Question

Petar Milin 2020-3-10

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https://ww2.mathworks.cn/matlabcentral/answers/510060-how-to-write-a-large-matrix-to-a-nc-file

编辑： Petar Milin 2020-3-15

I am trying to write a large matrix to a file using nccreate() and ncwrite(), but MATLAB is unfortunately crushing. Can you please provide a code example of how to write a matrix of, say 40K x 40x, in double precision?

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Answer 1

Jemima Pulipati 2020-3-13

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Here is a sample code which writes a 400 x 800 matrix to an NC file and retrieves the matrix from the file

and checks whether the data written matches or not using netcdf

numrow = 400;
numcol = 800;
my_data = rand(numrow,numcol);
ncid = netcdf.create('somefile.nc','NC_WRITE');
dimidrow = netcdf.defDim(ncid,'rows',numrow);
dimidcol = netcdf.defDim(ncid,'length',numcol);
varid = netcdf.defVar(ncid,'monthlypdsi','NC_DOUBLE',[dimidrow dimidcol]);
netcdf.endDef(ncid);
netcdf.putVar(ncid,varid,my_data);
netcdf.close(ncid);
ncid2 = netcdf.open('somefile.nc','NC_NOWRITE');
data_copy = netcdf.getVar(ncid2,0);
if isequal(my_data,data_copy)
    disp('Data match');
else
    disp('Data mis-match');
end

Hope it helps!

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Answer 2

Petar Milin 2020-3-15

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https://ww2.mathworks.cn/matlabcentral/answers/510060-how-to-write-a-large-matrix-to-a-nc-file#answer_420252

编辑：Petar Milin 2020-3-15

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Hi Jemima,

I see that your code is very explicit, taking all the steps. Meanwhile, I've tried this and it seems to work. However, I would really appreciate if you can advise whether you do see some (hidden) issues with my "shortened" version:

my_data = rand(400,600);
noX = size(my_data,1);
noY = size(my_data,2);
nccreate("file.nc","MyMatrix","Dimensions", {"x",noX,"y",noY},"FillValue","disable");
ncwrite("file.nc","MyMatrix",my_data);