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How do I sort filenames containing text and numbers in numerical order in MATLAB?

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Brad
Brad on 10 Oct 2017
Edited: Stephen Cobeldick on 18 Apr 2021 at 4:55
I have a series of .png files in a folder whose names are the following;
(A)Test_Nom_BAUD1.png
(A)Test_Nom_BAUD7.png
(A)Test_Nom_BAUD8.png
(A)Test_Nom_BAUD10.png
(A)Test_Nom_BAUD11.png
In reading the MATLAB documentation, I understand the dir function sorts strings in ASCII dictionary order. And since the files I'm using have no leading zeros, this is a problem. This is exactly what I'm seeing when I use the dir function:
A = dir('*.png');
(A)Test_Nom_BAUD1.png
(A)Test_Nom_BAUD10.png
(A)Test_Nom_BAUD11png
(A)Test_Nom_BAUD7.png
(A)Test_Nom_BAUD8.png
But what I need is this;
A = dir('*.png');
(A)Test_Nom_BAUD1.png
(A)Test_Nom_BAUD7.png
(A)Test_Nom_BAUD8.png
(A)Test_Nom_BAUD10.png
(A)Test_Nom_BAUD11.png
I know this can be done if the filenames contain only numbers.
But is it possible to sort these filenames (in numerical order) using existing text manipulation and sorting routines in MATLAB? If so, how?
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Accepted Answer

Cedric Wannaz
Cedric Wannaz on 10 Oct 2017
Edited: Cedric Wannaz on 10 Oct 2017
If, for any reason, you cannot install this function, you can sort your filenames as follows:
[~, reindex] = sort( str2double( regexp( {A.name}, '\d+', 'match', 'once' )))
A = A(reindex) ;
Note that it assumes that all files have the same base name. If you have to deal with various base names, then you need the function mentioned in the other answers, or to work a little more on the sorting.
  5 Comments
Stephen Cobeldick
Stephen Cobeldick on 21 Sep 2018
"You'll have to write a custom parsing routine to extract out the numbers you want into numerical vectors then sort them yourself."
You don't have to do that at all: natsortfiles handles multiple number values already. Just provide an appropriate regular expression, and it will work just fine:
>> C = {...
'RSN1112-KOBE-1.1_Node_Floor_Dsp.out',...
'RSN1111-KOBE-0.2_Node_Floor_Dsp.out',...
'RSN1112-KOBE-0.2_Node_Floor_Dsp.out',...
'RSN1111-KOBE-0.1_Node_Floor_Dsp.out',...
'RSN1111-KOBE-1.1_Node_Floor_Dsp.out',...
'RSN1112-KOBE-0.1_Node_Floor_Dsp.out'};
>> natsortfiles(C,'\d+\.?\d*') % alphanumeric sort
ans =
'RSN1111-KOBE-0.1_Node_Floor_Dsp.out'
'RSN1111-KOBE-0.2_Node_Floor_Dsp.out'
'RSN1111-KOBE-1.1_Node_Floor_Dsp.out'
'RSN1112-KOBE-0.1_Node_Floor_Dsp.out'
'RSN1112-KOBE-0.2_Node_Floor_Dsp.out'
'RSN1112-KOBE-1.1_Node_Floor_Dsp.out'

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More Answers (2)

KSSV
KSSV on 10 Oct 2017

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