Rearranging filenames with extension .number (Ordering)

I've got batches of data that end in MRDC.number (MRA slices e.g. i3078011.MRDC.205) and I want to order them by filename extensions i.e. MRDC.20,MRDC.21,MRDC.22,MRDC.23

Trouble is sort_nat for example reads the initial numbers not the extension

They go from MRDC.1 to MRDC.200ish ,but may vary

I've attached a typical filename cell array.

Cheers

[William]

This is a far as I've got

ext=char(zeros(size(filen)));
name=char(zeros(size(filen)));
for i = 1:size(filen)
[~,name(i),ext(i)] = fileparts(char(filen(i))); 
end

Answer 1

[Guillaume]

Building up on Ingrid's answer and your code, this will sort the extensions numerically, regardless of the filename:

ext = regexp(filen, '(?<=\.)\d+$', 'match', 'once');
[~, order] = sort(str2double(ext));
filen = filen(order)

I use a regular expression instead of fileparts so I can get rid of the . as well.

Answer 2

[Ingrid]

if all your filenames have the same length (which seem to be the case for the file in attachment) you could do this

fin = cellfun(@(x) x(15:end),filen,'UniformOutput',false);
fin = str2double(fin);
[~,idx] = sort(fin);

sortedFileNames = filen(idx);

[Ingrid]

alternativaly, if the size of the filename is not the same for all files you could use this

fin = cellfun(@(x) regexp(x,'\.','split'),filen,'UniformOutput',false);
fin = cellfun(@(x) x{end},fin,'UniformOutput',false);
fin = str2double(fin);
[~,idx] = sort(fin);

sortedFileNames = filen(idx);

Answer 3

[Stephen23]

There are several natural order sorting functions on MATLAB File Exchange, and they often use file-names in their examples... but they all suffer from the same problem: that extension separator character just keeps getting in the way!

To avoid this problem I created natsortfiles, which sorts the file-names and file-extensions separately. Take a look at the code and you will find it easy to adapt for your purposes.

It never occurred to me that someone might want to sort only by file-extension, but that would be a useful option to add...

Alternatively, because the extensions consist entirely of digits, simply split these from the names and sort them numerically:

>> load('filenames.mat')
>> [pth,nam,ext] = cellfun(@fileparts,filen,'UniformOutput',false);
>> [~,idx] = sort(cellfun(@(s)sscanf(s,'.%i'),ext));

This uses the built-in fileparts function, so it is not depended on the file-name lengths or anything like that, and the sscanf call allows us to neatly ignore the period character. Two lines of code and you have your sort index!