How to load files identified by the matlab function of "dir"?

I have many files in a folder named "mat_files". What I want to do is to load the files and get their values. Below is my code:

a = dir('mat_files');
for i = 3:length(a);  
    filename = a(i).name;
    load strcat('mat_files/', filename);
end;

This is the error:

Error using load
Unable to read file 'filename': no such file or directory.

When I type a(3).name in the command window, I get the correct filename of "ex0219.mat". Of course, I can load the data by typing "load ex0219.mat". Clearly load a(3).name does not work. I also tried load (a(3).name), which does not work either.

[sixwwwwww]

You should give full path in dir if the MATLAB current folder is not same as the folder you want to access and also specify which file types you want to read (See my anwser below) otherwise MATLAB will read file information for all files in that folder and will be difficult for you to read/load few required files later on

[Leon]

Thank you so much for the tip. I missed the path of the files when using load. But why

load strcat('mat_files/', filename) ;

does not work either?

[sixwwwwww]

rewrite it like this:

load(strcat('mat_files/', filename));

Answer 1

[Image Analyst]

See the second code example in the FAQ: http://matlab.wikia.com/wiki/FAQ#How_can_I_process_a_sequence_of_files.3F

A smiple modification gives you the answer:

myFolder = 'C:\users\leon\documents'; % or whatever.
if ~isdir(myFolder)
  errorMessage = sprintf('Error: The following folder does not exist:\n%s', myFolder);
  uiwait(warndlg(errorMessage));
  return;
end
filePattern = fullfile(myFolder, '*.mat');
matFiles = dir(filePattern);
for k = 1:length(matFiles)
  baseFileName = matFiles(k).name;
  fullFileName = fullfile(myFolder, baseFileName);
  fprintf(1, 'Now reading %s\n', fullFileName);
  storedStructure = load(fullFileName);
  % Now do whatever you need to do with the structure you recalled.
end

[Leon]

Thank you for the code. Glad to learn the use of "fullfile". It works flawlessly!

Answer 2

[sixwwwwww]

you should read files like this:

directoryString = 'YourDirectory';
files = dir(strcat(directoryString,'*.mat'));                                                   
names = {files.name}

I hope it helps. Good luck!

[Leon]

Thank you for the reply. The step of identifying filenames works fine. What gave me trouble is the step of loading the files. So how do I load the files with the names of "names"?

[sixwwwwww]

you can do it as follow:

for i = 1:length(names)
    load(strcat(directoryString, names{i}))
end

Is it working now?

[Leon]

Thank you! Unfortunately, I still get an error, after I tried:

load (strcat('mat_files/', filename));

===

Argument must contain a string.

Error in line 18: load (strcat('mat_files/', filename));

[sixwwwwww]

what you get by following command:

class(filename)

[Leon]

>> class(filename)

ans =

cell

>> strcat('mat_files/', filename)

ans =

'mat_files/ex0209a.mat'

[sixwwwwww]

that's the problem. It should be 'char' type. Can you check what is within filename. Try

filename{1} and what you get?

[Leon]

>> filename{1}

ans =

ex0209a.mat

After I replace filename with filename{1}, it is working now. Thank you so much!

[sixwwwwww]

you are wlecome