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Merging contents of multiple MAT files

Asked by Multiplexer on 25 Oct 2018
Latest activity Commented on by Multiplexer on 29 Oct 2018
Hello,
I got a collection of MAT files (generated by External Mode data archiving) that have names such as below and their count can go into 1000's: - MyMatFile_0.mat - MyMatFile_1.mat (...) - MyMatFile_2999.mat - MyMatFile_3000.mat
What i want to achieve is to merge all the arrays from inside the MAT files vertically together (like [MyMatFile_0.mat ; MyMatFile_1.mat ... ] and save that new single array to a spearate MAT file or simply leave it in workspace.
So for, example, with the files I'm attaching, each of them contains a 20x2 double array and I want to merge them together to make one MAT file with 60x2 double array.
Also, this batch of files is generated per each experiment i do and for each experiment the total number of MAT files may vary and the amount of elements in array in each MAT file also may vary (but there will be always 2 columns).
Any help is appreciated.

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1 Answer

Answer by Stephen Cobeldick on 25 Oct 2018
Edited by Stephen Cobeldick on 25 Oct 2018
 Accepted Answer

To read the files in the correct order download my FEX submission natsortfiles:
Then all you need is this (the input and output files are attached):
D = 'path to the folder where the files are saved'
S = dir(fullfile(D,'TestLog_*.mat'));
N = natsortfiles({S.name}); % download from FEX.
C = cell(1,numel(N));
for k = 1:numel(N)
T = load(fullfile(D,N{k}));
C(k) = struct2cell(T);
end
M = vertcat(C{:});
save('TestLog.mat','M')
This will work for any number of .mat files, with a few conditions:
  • each .mat file contains only one variable.
  • the output file is in a different folder or does not match the dir filename string (otherwise you could end up accumulating the same data repeatedly).

  7 Comments

Is this the way you meant to modify data? Each MAT file now contains two variables and the variable name is exactly same between each MAT file.
I started modifying the code but i messed something up big time. Instead of doing merge it started copying same file over and over again.
D = 'path to the folder where the files are saved'
S = dir(fullfile(D,'TestLog_*.mat'));
N = natsortfiles({S.name}); % download from FEX.
C = cell(2,numel(N));
for k = 1:numel(N)
T = load(fullfile(D,N{k}));
C{1,k} = T.Excite;
C{2,k} = T.Response;
end
M = vertcat(C{:});
save('TestLog.mat','M')
"Is this the way you meant to modify data? Each MAT file now contains two variables and the variable name is exactly same between each MAT file."
Yes, that is perfect. It will make your code much simpler. Here is some code that reads your new sample files, and follows the requirements that you gave in your earlier comment:
D = 'path to the folder where the files are saved';
S = dir(fullfile(D,'TestLog_*.mat'));
[~,X] = natsortfiles({S.name}); % download from FEX.
S = S(X); % sort the files into alphanumeric order.
for k = 1:numel(S)
T = load(fullfile(D,S(k).name));
S(k).Excite = T.Excite;
S(k).Response = T.Response;
end
Excite = vertcat(S.Excite);
Response = vertcat(S.Response);
save('TestExcite.mat', 'Excite')
save('TestResponse.mat','Response')
Thank you very much!

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