How do I access a folder that is inside the current folder while running a function?

I am writing a function that in different steps needs to access 1 or 2 files in different folders. The function will look something like this:

function Calculation = calc(n)

where n is the name of the file. Each of the folders will have one file named "N" and I want the program to go through each file and get the image data for that file.

[Walter Roberson]

Is n the name of the folder or the name of the file or the name of the combination?

[Sulaiman Alvi]

n is the name of the file. there is an "n" file in each of the folders that I am trying to access and I want to access each of them.

Answer 1

[Walter Roberson]

Presuming that n holds the name of the folder

this_N_name = fullfile(n, 'N');   %N has no extension??
this_data = imread(this_N_name);   %imread is not going to be happy with there not being an extension though

[Sulaiman Alvi]

the extention for all of these files is .bmp

[Walter Roberson]

function all_data = fetch_data(n)
  dirinfo = dir('*');        %find everything
  dirinfo = dirinfo([dirinfo.isdir]); %select only directories
  file_count = 0;   
  for K = 1 : length(dirinfo)
    this_file = fullfile(dirinfo(K).name, n);
    if exist(this_file, 'file')
      try
        this_data = imread(this_file);
        file_count = file_count + 1;
        all_data{file_count} = this_data;
      catch ME
        fprintf('file "%s" was not valid image file, skipped it', this_file);
      end
    end
  end
end

Returns a cell array of images, which you could then loop through to do your calculations. You would need to change it slightly if you want the file names returned along with the content. This code does not warn for directories that do not have a copy of the file, only for cases the file exists but could not be read as an image.

[Sulaiman Alvi]

Ok thanks a lot. How do I retrieve the cell array?

[Walter Roberson]

For example,

retrieved_data = fetch_data('Q39.bmp');
for K = 1 : length(retrieved_data)
  imshow(retrieved_data{K});
  pause(0.05);
end

[Sulaiman Alvi]

Hey. I ended up writing my own code based on what you gave me. I wanted to test it but it didnt work. Can you take a look at it?

function I3value = I3(f1)
A = double(imread(f1,'bmp'));
I3value = (A);
imshow(I3value)

Above is what I want to do with the file.

Here is the rest of the code:

function nvalue = calcStokes(n)
full_name = fullfile('I0', n.bmp);
I3value = I3(full_name);
disp(I3value)

I0 is the folder i wanted to get it from, and I need to get a file with the name 15 and the bmp format. How can I fix this?

[Walter Roberson]

full_name = fullfile('I0', sprintf('%d.bmp', n));

By the way, when you are working with images, in a number of contexts MATLAB pays attention to whether the array is uint8 or double. When it is uint8 MATLAB expects the values to be in the range 0 to 255; when it is double MATLAB expects the values to be in the range 0 to 1. I recommend you use

A = im2double(imread(f1,'bmp'));

instead of using double()