How to combine the multiple .mat files of ecg to get a single file.

I have 23 files(in .mat) of atrial fibrillation database. i want to combine all these mat files to get a matrix of (23*2500) where 2500 is the samples of each .mat files and 23 is the no of records or no. of files.

Please help!

[Stephen23]

What size do the .mat file contents have?

What are the names of the variable/s in the mat files? (hopefully they are all the same!)

What sequence do the filenames have?

[SHRESTH GUPTA]

i have attached a single .mat file and it has 1 row and 2500 samples as column.

the names are 04015m.mat, 04018m.mat etc.

Answer 1

[Stephen23]

This should get you started:

D = 'path to the folder where the files are saved';
S = dir(fullfile(D,'*.mat'));
for k = 1:numel(S)
    F = fullfile(D,S(k).name);
    T = load(F);
    S(k).data = T.val;
end
M = vertcat(S.data);
save(fullfile(D,'merged.mat'),'M')

See also: https://www.mathworks.com/help/matlab/import_export/process-a-sequence-of-files.html

[SHRESTH GUPTA]

Thank you so much stephen sir!

[Stephen23]

@SHRESTH GUPTA : please remember to accept my answer!

[SHRESTH GUPTA]

its giving error as:

Reference to non-existent field 'val'.

Error in loadf (line 6)

S(k).data = T.val;

[Stephen23]

"Reference to non-existent field 'val'."

Your uploaded .mat file contains one variable named val, so I assumed that every file has the same variable name (answering your question is a lot easier if you give this kind of information, then we don't have to guess important details like this).

Here is a simple adaption of my answer that will work regardless of the variable name, it assumes that each .mat file contains exactly one variable. Replace the two lines with T in them with these two:

C = struct2cell(load(F));
S(k).data = C{1};

Answer 2

[Image Analyst]

Try this:

folder = pwd; %'path to the folder where the files are saved';
fileList = dir(fullfile(folder, '*.mat'));
numFiles = numel(fileList);
fileCounter = 0;
allValData = [];
for k = 1 : numFiles
	fullFileName = fullfile(folder,fileList(k).name);
	% Skip output file if it already exists.
	if contains(fullFileName, 'allValData.mat', 'IgnoreCase', true)
		continue;
	end
	fprintf('Reading %s (#%d of %d)...\n', fullFileName, k, numFiles);
	storedStructure = load(fullFileName);
	% If storedStructure has a field called val, concatenate it.
	if isfield(storedStructure, 'val')
		allValData = [allValData; storedStructure.val];
		fileCounter = fileCounter + 1;
	else
		fieldnames(storedStructure) % Report what fields there are to the command window.
		warningMessage = sprintf('WARNING : There is no Val field in file %d of %d:\n%s', k, numFiles, fullFileName);
		fprintf('%s\n', warningMessage);
		promptMessage = sprintf('%s\nDo you want to Continue processing,\nor Quit processing?', warningMessage);
		titleBarCaption = 'Continue?';
		buttonText = questdlg(promptMessage, titleBarCaption, 'Continue', 'Quit', 'Continue');
		if contains(buttonText, 'Quit', 'IgnoreCase', true)
			break;
		end
	end
end
fprintf('Concatenated %d of %d files.  Skipped %d files.\n', fileCounter, numFiles, numFiles - fileCounter);
fullOutputFileName = fullfile(folder, 'allValData.mat');
save(fullOutputFileName, 'allValData')

Did it work, or if not, did you see anything unusual?