sort_nat: Natural Order Sort

Sort strings in natural order.

Description

Natural order sorting sorts strings containing digits in a way such that the numerical value of the digits is taken into account. It is especially useful for sorting file names containing index numbers with different numbers of digits. Often, people will use leading zeros to get the right sort order, but with this function you don't have to do that. For example, with input of

{'file1.txt','file2.txt','file10.txt'}

a normal sort will give you

{'file1.txt','file10.txt','file2.txt'}

whereas, sort_nat will give you

{'file1.txt','file2.txt','file10.txt'}

Acknowledgements

This file inspired Lilo : Fast And Pixel Accurate Stitching For 2 D Tiles and Customizable Natural Order Sort.

• MATLAB release: MATLAB 7.0.4 (R14SP2)

[Pete]

 

[Ekaterina]

Sorry, I am a beginner in MATLAB and I am not sure what the input arguments in these function mean. There are many input argument.... I have a struct array (conists of files with names ex.123_1, 123_2, etc) A <3000*1> struct and I want to sort it according to name of files which are there. How shoud I use this function... Please help me.. best wiches Katya

[salvatore savo]

thanks a lot!!! great

[Harish S]

Excellent

[Nopparat]

 

[Muhammet]

 

[Caleb]

Just what I needed, thanks!

[Shamir Alavi]

I have wasted a lot of time trying to properly sort my image files for my image processing project before I surfed on to this code. And mathworks web tutorial on this is totally flawed. Great work! Certainly deserves a 5 star.

[Damon Bradley]

Excellent work. Saved me a much time and headache with some data analysis over here at NASA. Thank you!

[Damon Bradley]

 

[Ben]

This is great! Better to include it in the Matlab!

[Johanna]

 

[Jun]

Many thanks, save me time and effort to write my own code to crack this problem

[Carsten]

 

[Edwin Carter]

Great, works straight off in Octave too.

[Evgeny Pr]

Douglas Schwarz,
You offered the perfect solution for case-insensitive sorting.
Thank you!

[Douglas Schwarz]

Evgeny, you must be the first person to use descending order and the index. You are quite right, it's a bug and I thank you for identifying it. I fixed it in a slightly different way and just uploaded the new version.

To do case-insensitive sorting you can just do this:
c = {'a1', 'a2', 'a10', 'b1', 'X1', 'A10'};
[unused,index] = sort_nat(lower(c));
cs = c(index);

I want sort_nat to work the same way as sort and since sort doesn't do case-insensitive sorting I left that out of sort_nat as well.

Regards,
Doug

[Evgeny Pr]

This code not entirely correct:
if strcmpi(mode,'ascend')
cs = c(index);
else
cs = c(index(end:-1:1));
end

Output argument INDEX does not change depending on the sort order.

Better to do so:
if strcmpi(mode, 'descend')
index = flipud(index);
end
cs = c(index);
index = reshape(index, size(cs)); % same as C array dimension

[Evgeny Pr]

Hi! Very good function and coding!
I could not write such a elegant and fast function. :)

One question:
You would not want to make sort mode a case-insensitive?

For Example:
c = {'a1', 'a2', 'a10', 'b1', 'X1', 'A10'}

Case-sensetive sort:
cs = {'A10', 'X1', 'a1', 'a2', 'a10', 'b1'}

Case-insensitive sort:
cs = {'a1', 'a2', 'a10', 'A10', 'b1', 'X1'}

[Oscar]

 

[Pete]

Excellent. 5 stars.

I think I ran into the need for a descending sort because I was looking to search through various files with timestamps in their name for the most recent entry (of something-or-other).

Anyway, good work.

[Douglas Schwarz]

Pete, I'm not sure sorting in descending order will be used very often, but, as you say, it's easy to add so why not? I chose to do it in a slightly different way, but it works the way you want. Thanks for the suggestion. Update should appear soon.

[Pete]

Good work.

Is it just me though or would this not benefit from being able to specify the direction? This would be as simple as:

function [cs,index] = sort_nat(c,varargin)

... <entire code>

if nargin>1
if strcmpi(varargin{1},'descend')
index = flipud(index);
cs = c(index);
end
end

[Adam Baker]

I wish I'd found this sooner!

[Greg Fichter]

Nifty, thanks.

[Nikola Toljic]

Thanks

[Gang Xu]

Nice! Thanks

[Hans van Dijk]

Great, just what I needed.

[F Moisy]

Perfect. Should be included in R2007a!

[Mike Palumbo]

Great, much better than another file on the exchange "sortn", sortn froze when trying to sort over 6000 strings, this sort did it just fine in about a second.