writing large 3D .mat file into a .xls file

I am trying to export a 3D .mat file into an .xls or even a .txt file, but I cant do that as the load/write functions work only for 2D .mat files. The problem is that the file is large (512*512*313) [ I get the 0x800A03EC error]. Excel as far as I know cant handle more than 256 columns, and I cant transpose this directly as it is a 3D array. Any ideas?

[Matt Kindig]

How are you going to use the .xls/.txt file afterwards? Do you need it to input into another program, or just for storage in a non-binary format?

The reason I ask is because you can't (as far as I know) directly do this in a text file, but you can structure the text file as a 2D matrix with delimiters for each page (the 313 dimension). Your file could look something like this, perhaps.

==Page 1===
1,2,3,4,.....  
2,4,5,1,.....
....
==Page 2===
3,3,5,5,....
5,2,6,7.....
....
==Page N===

[Salam]

The 3D file I am trying to export will eventually be analyzed and some plots will be made. I need to the file to have some high resolution data about what I am working with. I dont mind exporting it to text, then copying it into .xls file, but I cant find my way around the fact that it is a huge 3D array.

[Sven]

Salam, Matt's right... the big question here is what you want to do with the data after it's exported. There are some ways you could represent your 3D data in excel (putting each "page" on a separate spreadsheet, putting each "page" below the previous "page" on a single spreadsheet, etc), but none of these ways will make it very pleasant to deal with the actual excel file.

This isn't a problem that "MATLAB can't export 3D data to excel", it's more a case of "excel isn't well suited to 3D data".

[Salam]

The .mat file holds some voxel-based data. I need to find certain groupss of voxels/cells and plot the values, analyze the numbers.

Answer 1

[Sven]

Salam,

Here's some code that will at least get your data into excel in some form. You're right that excel has the limitation of 256 columns. Therefore I've fitted each 512-by-512 page into the available space by slicing it in half and storing two 512-by-256 pieces one above the other. I've also chosen to represent the 3rd dimension using different sheets in excel. I'm afraid that this is about the best that can be done when trying to put 3D data into excel:

A = rand(512,512,313);
A_narrow = cat(1, A(:,1:256,:), A(:,257:end,:));
for i = 1:size(A,3)
  xlswrite('myfile.xls',A_narrow(:,:,i),['page_' num2str(i)], 'A1')
end

Does this at least run through without error?

[Salam]

It produces a file with a 1024*256 sheet. Looking at this makes me re-think about if I really need to do this. Exporting CT voxels very-specific-kinda -of-data is massively beneficial but not sure if it is as beneficial as I am hoping.

[Sven]

It will actually produce a file with 313 separate 1024*256 sheets, but that's what we've been getting at this whole time... the more clearly you can define exactly what you mean by "do analysis of 3D voxels in excel", the more you'll see that excel really isn't the right tool for the job :)

Anyway, I hope that my answer at least answered your original question of how to put 3D data into excel in the first place.

[Salam]

I do thank you. If you have any suggested tool other than Excel, I will be thankful.

[Sven]

Ha, my suggestion would be MATLAB ;)

It's really quite well suited to 3D data, and I'd bet that if you can describe clearly what you mean by "analysis on the voxels", there will be plenty of help that you can get right on this forum for how to get MATLAB to perform such analysis.