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How to generate sequences from two vectors using rowfun

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Hi,
I am trying to generate sequences for which starting values and last values+1 are contained in vectors, without using for-loop. Because there is a lot of data to process, doing for-loop is unfortunately not feasible. As the output, I want to have all the sequences to be concatenated into one vector. I think rowfun can help me here, but so far I have not been successful. If someone can give me a helping hand, I would be grateful.
This is an example;
x = [1,6,12]'; y = [5,10,13]';
the output I wish to obtain: z = [1,2,3,4,6,7,8,9,12];
I imagine it should be something like;
inputvecs = table(x,y);
z = rowfun(@seqgen,inputvecs)
How should the function seqgen look in this case? Should concatenation within the function?
Thank you very much for your help.
Etsuko

Accepted Answer

Stephen23
Stephen23 on 13 Jul 2016
Edited: Stephen23 on 13 Jul 2016
You could use arrayfun instead:
>> x = [1,6,12]; y = [5,10,13];
>> cell2mat(arrayfun(@(a,b)a:b-1, x,y,'UniformOutput',false))
ans =
1 2 3 4 6 7 8 9 12
or
>> tmp = arrayfun(@(a,b)a:b-1,x,y,'UniformOutput',false);
>> horzcat(tmp{:})
ans =
1 2 3 4 6 7 8 9 12
Note that the inputs must be horizontal vectors.
  2 Comments
Etsuko
Etsuko on 13 Jul 2016
Edited: Etsuko on 13 Jul 2016
Thank you so much for your help, Stephen and Andrei!
Here I compared time for these three methods;
>> x = [1,6,12]; y = [5,10,13];
>> tic; cell2mat(arrayfun(@(a,b)a:b-1, x,y,'UniformOutput',false)); toc
Elapsed time is 0.008368 seconds.
>> tic; tmp = arrayfun(@(a,b)a:b-1,x,y,'UniformOutput',false);horzcat(tmp{:}); toc
Elapsed time is 0.000757 seconds.
>> tic; a = (min(x):max(y))';[ii,~] = find(bsxfun(@ge,a,x)&bsxfun(@lt,a,y));out = a(ii);toc
Elapsed time is 0.003983 seconds.
Thank you!
Stephen23
Stephen23 on 13 Jul 2016
Edited: Stephen23 on 13 Jul 2016
@Etsuko: note that to get meaningful timing values for such quick functions, it is recommended to repeat the process a few hundred or thousand times.

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More Answers (1)

Andrei Bobrov
Andrei Bobrov on 13 Jul 2016
Edited: Andrei Bobrov on 13 Jul 2016
x = [1,6,12]; y = [5,10,13];
a = (min(x):max(y))';
[ii,~] = find(bsxfun(@ge,a,x)&bsxfun(@lt,a,y));
out = a(ii);

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