combine a number of files together? cat,vertcat and horzcat do not work...

Hey all!

I have 254 files named blah_blah_001 until blah_blah_254. Each file has 723 x 3127 dimension and I want to combine all to create a 723 x 3127 x 254 matrix. I have tried loops but I am not sure how to write so that each file number is with 3 digits. Here is my attempt:

all = NaN(723,3127,254);

% attempt to put all arcs together..

for i=1:254;
    for arc = 001:254;
    all(:,:,i) = [TJJ_arc_(arc)]

      end;
  end;

After this I wish to calculate a nanmean to get 723 x 254...

Can someone help me?

[Azzi Abdelmalek]

What type of files?

[Michael]

They are included in a single .mat file. For example, blah.mat is loaded with all 254 files...

Answer 1

[Geoff Hayes]

Use sprintf to create the file name on each iteration

 allData = NaN(723,3127,254);

 for k=1:254

     % create the file name
     filename = sprintf('TJJ_arc_%03d.mat',k);

     % load the data
     data = load(filename);

     % save the data
     allData(:,:,k) = data;

 end

NOTE that all is a built-in MATLAB function so your code should avoid using this as a variable name.

NOTE also how I replaced your iterator i with k. i and j are used in MATLAB as the representation of the imaginary number, so it is good practice to avoid using them in for loops.

Try the above and see what happens!

[Michael]

Thanks Geoff, however, it doesn't seem to work exactly. It complains that 'Error using load. Unable to read file TJJ_arc002: No such file or directory.'.

I tried removing .mat but it didn't work. Do you know what I should change? maybe it's because the files are all loaded into one .mat file and do not have the .mat extension?

[Geoff Hayes]

Michael - what do you mean by the files are all loaded into one .mat file? In your question, you stated that there were 254 files with a prefix and a 3 digit suffix. Do you really mean that you have 254 (723 x 3127) variables all loaded into a single mat file?

[Michael]

Yes I did, sorry for the confusion. I realised later after submitting the question. I managed to sort it like so:

adata = NaN(723,3127,254);

 for k=1:254
     k
     tic

     % create the file name
     filename = sprintf('TJJ_arc%03d',k);
     load('TJJ.mat',filename);
     a = eval(filename);
     % load the data
     %data = load(filename);

     % save the data
     adata(:,:,k) = a;
     toc

     clearvars -except adata

 end

Thanks for your help though, Geoff! you put my in the right direction.

[Geoff Hayes]

Cool. You may want to change the above filename variable to varname so that it is clear that a variable named whatever is being loaded rather than a file.

Answer 2

[Michael]

Thanks Geoff, however, it doesn't seem to work exactly. It complains that 'Error using load. Unable to read file TJJ_arc002: No such file or directory.'.

I tried removing .mat but it didn't work. Do you know what I should change? maybe it's because the files are all loaded into one .mat file and do not have the .mat extension?