MATLAB, Consecutive Numbers

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MATLAB >> Consecutive Numbers

by Nichola » Wed, 13 May 2009 23:56:01 GMT

Hi. Given a series of sorted numbers, is there a function in MATLAB that recognizes the consecutive values?

For example:
1, 2, 3, 4, 5, 10, 11, 13
Should be divided into:
1:5
10:11
13

I've written a function that goes over the values and compares the number before and after a certain element, but I'm quite sure there's a faster and better way.

Thanks a lot.
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MATLAB >> Consecutive Numbers

by Matt Fig » Thu, 14 May 2009 00:11:01 GMT


Look at:
x = [1 2 3 4 5 10 11 13];

D = ~~([1 diff(x - (1:length(x)))]) % Where are the ones?
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MATLAB >> Consecutive Numbers

by Nichola » Thu, 14 May 2009 00:23:02 GMT


Thanks. I see your point, but could you please explain the ~~ for me? Thanks.
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MATLAB >> Consecutive Numbers

by Matt Fig » Thu, 14 May 2009 00:31:01 GMT


This makes D a logical vector. Actually this is not strictly necessary, depending on how you would proceed from here. I might do something like this:


x = [1 2 3 4 5 10 11 13 14]
F = diff(find([1 diff(x - (1:length(x)))]));
mat2cell(x,1,[F length(x)-sum(F)])
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MATLAB >> Consecutive Numbers

by kannadaraj1 » Thu, 11 Jun 2009 03:37:40 GMT

Thanks very much
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MATLAB >> Consecutive Numbers

by Siyi » Thu, 11 Jun 2009 04:36:48 GMT


Essentially the same method as Matt's but a oneliner:

mat2cell(x,1,diff([0,find(diff(x) ~= 1),length(x)]))
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MATLAB >> Consecutive Numbers

by Bruno Luong » Thu, 11 Jun 2009 14:45:02 GMT

Or using SplitVec on FEX: http://www.mathworks.com/matlabcentral/fileexchange/24255


a =

1 2 3 4 5 10 11 13


ans =

[1x5 double] [1x2 double] [13]

% Bruno
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MATLAB >> Consecutive Numbers

by Sprinceana » Thu, 11 Jun 2009 15:51:02 GMT


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MATLAB >> Consecutive Numbers

by PopV Visitkul » Thu, 09 Jul 2009 18:40:17 GMT

Hi Matt,

Would it be possible to explain the principle behind the code by any chance please? What I really like about it is that it managed to group the consecutive numbers really nicely in a large file. What I am trying to do now is grouping bunches of zeros and ones from a random mixture of zeros and ones sequence. I slightly modified your code for do it yesterday. However it seems to only group the the zeros together while leaving all the ones ungrouped. This is because i didn't know what i was doing. Your explanation would be highly appreciated.

Many thanks,
Viput
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