MATLAB: Sorting an array of strings based on number pattern

natsortnatsortfilespatternsequencesortstrings

I'm looking for an efficient way to solve the following issue:

Typically I read out all files in a directory that match a certain pattern by means of the dir function:

dirFiles = dir('Common_*_common.ext');
fileNames= {dirFiles.name};

This does what it is supposed to do and gives me a nice cell array with files I need to load.

However, the pattern is of the format 0, 1, 2, …, 8, 9, 10 and the order of my fileNames comes out as 0, 10, 1, …, 7, 8, 9. Unfortunately, changing the filenames themselves to 00, 01, 02, …, 10 is not an option. Is there an efficient way to sort such arrays to the correct format?

Of course this should also hold when the sequence increases to larger numbers (e.g. 0, 1, 2, …, 29, 30, 31).

Best Answer

Ok, I should've searched better...

Problem solved with a PotW tool by Stephen Cobeldick.

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MATLAB: Order CSV based on underlying timestamp OR using correct number

Fixed it using:

[r inx]=sort({csvFiles.date});
csvFiles = csvFiles(inx);

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.

Best Answer

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MATLAB: Order CSV based on underlying timestamp OR using correct number

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

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