在Matlab中将2d矩阵导出为三元组格式CSV文件的最快方法

Question

I want to convert a 2d matrix, for example:

10  2
3   5

to a (row,col,value) CSV file, for example:

1,1,10
1,2,2
2,1,3
2,2,5

is it possible to do it in a single Matlab command?

Answer 1

I didn't find a way with a single command, but try the following code:

[i1,i2] = ind2sub(size(A),1:numel(A));
csvwrite('test.csv',[i2',i1',reshape(A',numel(A),1)]);

The output is:

type test.csv

1,1,10
1,2,2
2,1,3
2,2,5

Answer 2

Assuming A to be the input matrix, two approaches can be suggested here.

fprintf based solution -

output_file = 'data.txt'; %// Edit if needed to be saved to a different path
At = A.';  %//'
[y,x] = ndgrid(1:size(At,1),1:size(At,2));
fid = fopen(output_file, 'w+');
for ii=1:numel(At)
    fprintf(fid, '%d,%d,%d\n',x(ii),y(ii),At(ii));
end
fclose(fid);

---

dlmwrite based approach -

At = A.';  %//'
[y,x] = ndgrid(1:size(At,1),1:size(At,2));
dlmwrite(output_file,[x(:) y(:) At(:)]);

Some quick tests seem to suggest that fprintf performs better across varying input datasizes.