MATLAB: How to sort the order given by ‘dir’ command ??

commanddigital image processingdirimage analysisimage processing

I am reading the images from a folder by using the below code

   [folder1] = uigetdir();
   f=dir(folder1);
   for k=1:size(f,1)-2
    file_n=f(k+2).name;
   end

The images in the folder are "test_base1", "test_base2", …. but the order in which 'dir' taking is "test_base1","test_base10","test_base2".. I understood that the command is taking ascii-betical order.. I have gone through the previous questions and answers. It seems complicated. Can any one give a good solution to sort the order of Images after using "dir"

Best Answer

file={'test_base1','test_base10','test_base2'}
[idx,idx]=sort(cellfun(@(x) str2num(char(regexp(x,'\d*','match'))),file))
new_file=file(idx)

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MATLAB: Issues with sort_nat and natsortfiles; error improper matrix reference

natsortfiles returns a cell array, not a structure. Just like sort it returns the same cell array that was provided to it, just sorted into a particular order. Do you expect sort to return a structure when you pass it a cell array? As I wrote in the help quite clearly, natsortfiles has output " Y = Cell of Strings, X with all strings sorted into natural-order."

Not only did I state that the output is a cell array I also gave several examples in the FEX description, in the M-file help, and also in the HTML documentation, such as this simple example:

D = 'natsortfiles_test'; % directory path
S = dir(fullfile(D,'*.txt')); % get list of files in directory
N = natsortfiles({S.name}); % sort file names into order
for k = 1:numel(N)
  fullfile(D,N{k})
end

Notice that in all of those examples the output is a cell array (just like the input is). But you are trying to access the output as if it was a structure with fields:

cx(q).name

...but a cell array does not have fields! So once you stop trying to access the cell array as if it was a structure, and start to access the cell array using cell array indexing (just like the examples I wrote show) then that error will disappear.

MATLAB: Looping to read image

My File Exchange submission natsortfiles was written exactly for solving this problem:

http://ww.mathworks.com/matlabcentral/fileexchange/47434-natural-order-filename-sort

It sorts a cell array of strings into the order that you require, by considering all numeric values in the strings instead of just the naive character order (like sort does). You can use it very simply:

>> B = {'test2.m'; 'test10-old.m'; 'test.m'; 'test10.m'; 'test1.m'};
>> natsortfiles(B)
ans =
  'test.m'
  'test1.m'
  'test2.m'
  'test10.m'
  'test10-old.m'

whereas the inbuilt sort returns the strings sorted according to their character order:

>> sort(B)
ans =
  'test.m'
  'test1.m'
  'test10-old.m'
  'test10.m'
  'test2.m'

To use this with your filenames, simply extract the filename strings from the output of dir like this:

hasil = dir('*.jpg');
names = natsortfiles({hasil.name});
for k = 1:numel(names)
    out = imread(names{k});
    ... image processing here
end

Note that natsortfiles is a wrapper for this function, which you will also need:

http://www.mathworks.com/matlabcentral/fileexchange/34464-customizable-natural-order-sort

Best Answer

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MATLAB: Issues with sort_nat and natsortfiles; error improper matrix reference

MATLAB: Looping to read image

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