How to execute several mat file in a loop.

I have 5 mat files in a folder.

Battery_Power_280.mat

Battery_Power_300.mat

Battery_Power_320.mat

Battery_Power_340.mat

Battery_Power_360.mat

whenever executing loop, it's stopped and showing no such file directory(Error: Unable to read file 'Battery_Power_1.mat'. No such file or directory).

But it should run untill N,if does not get "Battery_Power_1"(k=1)then it sould go for next step (k=2).

Would you please light up about this ? If (k=280:20:360) then it executes successfully. But i want the k value (1:1:N)

CODE:

N=500;

C = cell(1,N);

for k = 1:1:N

F = sprintf('Battery_Power_%d.mat',k);

S = load(F);

C{k} = S.Data_BatteryPower.signals.values(:,1);

end

M = [C{:}];

Answer 1

[Voss]

To have k = 1 correspond to mat file 280, and k = 2 correspond to mat file 300, and so on, you can do this:

N=500;
mat_file_nums = 280:20:360;
C = cell(1,N);
for k = 1:1:N  
    F = sprintf('Battery_Power_%d.mat',mat_file_nums(k));
    S = load(F);
    C{k} = S.Data_BatteryPower.signals.values(:,1);
end
M = [C{:}];

[Arif Hoq]

Error:

Index exceeds the number of array elements (5).

Error in testing2 (line 5)

F = sprintf('Battery_Power_%d.mat',mat_file_nums(k));

In my folder it has 5 mat files. whenever k=6, then it shows this error. what can be the reason?

[Voss]

I guess N should be 5 then. Why is it 500?

[Arif Hoq]

actually i am thinking about more mat files,like 50 files. it can be more or less. so N should be a approximate value.

Your code is correct with definite files and filename.

But if i want to load all mat files(suppose, Battery_Power_10.mat,Battery_Power_13.mat,Battery_Power_18.mat,Battery_Power_25.mat) then showing error. because of index value k.

if I change this (mat_file_nums = 1:1:N;) then error happens.

[Voss]

If you try to load a mat file that does not exist, an error will occur and the code will stop execution. If you want the loop to continue instead, you can handle the error with try/catch or you can check that the mat file exists before you try to load it.

[Arif Hoq]

could you please share the "continue" systax or try/catch systax?

thank you.

[Voss]

To check for the files' existence:

N=50;
mat_file_nums = 115:5:360; % 50 numbers
C = cell(1,N);
for k = 1:1:N  
    F = sprintf('Battery_Power_%d.mat',mat_file_nums(k));
    if exist(F,'file')
        S = load(F);
        C{k} = S.Data_BatteryPower.signals.values(:,1);
    end
end
M = [C{:}];

To try/catch:

N=50;
mat_file_nums = 115:5:360;
C = cell(1,N);
for k = 1:1:N  
    F = sprintf('Battery_Power_%d.mat',mat_file_nums(k));
    try
        S = load(F);
    catch
        continue
    end
    C{k} = S.Data_BatteryPower.signals.values(:,1);
end
M = [C{:}];

[Arif Hoq]

got my expected solution. Thanks @Benjamin

Answer 2

[Image Analyst]

Try this:

folder = pwd;
filePattern = 'Battery*.mat';
fileList = dir(filePattern);
for k = 1 : length(fileList)
    [~, thisFileName, ext] = fileparts(fileList(k).name);
    % Optional user prompt to load the mat file, skip it, or quit.
    promptMessage = sprintf('Do you want to load file %d of %d:\n%s,\nor Quit processing?', ...
        k, length(fileList), thisFileName);
    titleBarCaption = 'Continue?';
    buttonText = questdlg(promptMessage, titleBarCaption, 'Load', 'Quit', 'Skip', 'Load');
    if contains(buttonText, 'Load', 'IgnoreCase', true)
        fprintf('\nLoading "%s".m.\n', thisFileName)
        S = load(thisFileName)
    elseif contains(buttonText, 'Quit', 'IgnoreCase', true)
        break;
    end
end

[Arif Hoq]

its working only for the last mat file. should i use cell array for all mat files ?

[Walter Roberson]

folder = pwd;
filePattern = 'Battery*.mat';
fileList = dir(filePattern);
saved_data = {};
for k = 1 : length(fileList)
    [~, thisFileName, ext] = fileparts(fileList(k).name);
    % Optional user prompt to load the mat file, skip it, or quit.
    promptMessage = sprintf('Do you want to load file %d of %d:\n%s,\nor Quit processing?', ...
        k, length(fileList), thisFileName);
    titleBarCaption = 'Continue?';
    buttonText = questdlg(promptMessage, titleBarCaption, 'Load', 'Quit', 'Skip', 'Load');
    if contains(buttonText, 'Load', 'IgnoreCase', true)
        fprintf('\nLoading "%s".m.\n', thisFileName)
        S = load(thisFileName);
        saved_data{end+1} = S;
    elseif contains(buttonText, 'Quit', 'IgnoreCase', true)
        break;
    end
end

Note that each entry in saved_data will be a struct with one field for each variable in the file.

[Image Analyst]

@Mohammad Ariful Hoq it works for all mat files, not just the last one. What you should do after the data is read into S is to call some function that processes S and returns results.

If you want, you can save all the data into a cell array like Walter showed above (unhide comments). But then you'll just have to have a second for loop to process all the data you've saved in the saved_data cell array. I think it's better to just do it all in one for loop. Is there some other reason why you'd need all the saved data after the loop exits???