using fopen, issue with the sequence files are opened

I am having a problem with fopen. I am opening a sequence of snapshots, however 1001 is being treated as the next in the sequence to 100. So fopen is opening files in the following order:

snapshot_100

snapshot_1001

snapshot_1002

snapshot_1003

...

snapshot_101

snapshot_1010

snapshot_1011

Is there a way to get these to open in the correct sequence? My code is as follows:

files=dir(fullfile(dirname, 'snapshot*'));
for i=1:numfiles    
  files(i).name=fopen(files(i).name,'r','n');
  fseek(files(i).name,264,'bof');
  [~,count]= fread(files(i).name,1,'int32');
  posdata{i}=fread(files(i).name,[3,N],'*float32','n');
  [~,count]= fread(files(i).name,1,'int32');
  posdata{i}=posdata{i}';
  x{i}=posdata{i}(1:N,1);
  y{i}=posdata{i}(1:N,2);
  z{i}=posdata{i}(1:N,3);
...

I cannot change the number of digits on the snapshots. Any help would be welcome.

[Walter Roberson]

Note: dir() returns the filenames in the order returned by the operating system. In MS Windows, the operating system returns the files in the order stored on the file system. Some of the file systems use byte-level sorting, but some of the less common MS Windows file systems use other orders (or no particular order.)

In short: you should not rely on the order of names returned by dir()

Answer 1

[Azzi Abdelmalek]

You can sort your files like this:

files={'snapshot_100'
'snapshot_1001'
'snapshot_1002'
'snapshot_1003'
'snapshot_101'
'snapshot_1010'
'snapshot_1011'}
[ii,jj]=sort(cellfun(@str2double,regexp(files,'\d+','match')))
files=files(jj)

[Azzi Abdelmalek]

[Nicolas commented]

Thanks for the help.

Nicolas, to add a comment click on [comment on this answer]

Answer 2

[Image Analyst]

Parse the filenames so that you extract the numbers into an integer array, then sort the array and get the indexes

[sortedNumbers, sortIndexes] = sort(numberArray);
% Then apply the same sorting order onto your filename array.
files = files(sortIndexes);

(Note: off the top of my head - not tested.)

Answer 3

[Walter Roberson]

There is a FEX contribution to sort filenames that contain embedded numbers.

[Nicolas]

FEX contribution?

[Azzi Abdelmalek]

File Exchange

[Walter Roberson]

http://blogs.mathworks.com/pick/2006/09/11/file1-file10-file2-sorting-problem-solved/