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From: Casey on 17 Jun 2010 15:13
I have an index matrix where each element in the first column is an ordered index number (possibly with duplicates), and the second column provides the number of times that the corresponding index is to be replicated. Basically, i want to create a single vector that replicates each element in the first column the number of times appearing in the second column.

For example, I have the following matrix:

1 3
2 2
3 2
3 3
4 1
5 1

And I want it to appear as follows:

1
1
1
2
2
3
3
3
3
3
4
5

Can anyone provide help doing this?

Thanks!
From: dpb on 17 Jun 2010 15:26
Casey wrote:
> I have an index matrix where each element in the first column is an
> ordered index number (possibly with duplicates), and the second column
> provides the number of times that the corresponding index is to be
> replicated. Basically, i want to create a single vector that replicates
> each element in the first column the number of times appearing in the
> second column.
>
> For example, I have the following matrix:
>
> 1 3
> 2 2
> 3 2
> 3 3
> 4 1
> 5 1
>
> And I want it to appear as follows:
>
> 1
> 1
> 1
> 2
> 2
> 3
> 3
> 3
> 3
> 3
> 4
> 5
....

Very crude straightahead ... ix is the above "dope" array...

x=[];for idx=1:length(ix),x=[x;ones(ix(idx,2),1)*ix(idx,1)];end

--
From: Casey on 17 Jun 2010 15:37
dpb <none(a)non.net> wrote in message <hvdt1n$3mh$1(a)news.eternal-september.org>...
> Casey wrote:
> > I have an index matrix where each element in the first column is an
> > ordered index number (possibly with duplicates), and the second column
> > provides the number of times that the corresponding index is to be
> > replicated. Basically, i want to create a single vector that replicates
> > each element in the first column the number of times appearing in the
> > second column.
> >
> > For example, I have the following matrix:
> >
> > 1 3
> > 2 2
> > 3 2
> > 3 3
> > 4 1
> > 5 1
> >
> > And I want it to appear as follows:
> >
> > 1
> > 1
> > 1
> > 2
> > 2
> > 3
> > 3
> > 3
> > 3
> > 3
> > 4
> > 5
> ...
>
> Very crude straightahead ... ix is the above "dope" array...
>
> x=[];for idx=1:length(ix),x=[x;ones(ix(idx,2),1)*ix(idx,1)];end
>
> --


PERFECT! THANKS!
From: us on 17 Jun 2010 15:48
"Casey " <cjd24060(a)yahoo.com> wrote in message <hvds42$18t$1(a)fred.mathworks.com>...
> I have an index matrix where each element in the first column is an ordered index number (possibly with duplicates), and the second column provides the number of times that the corresponding index is to be replicated. Basically, i want to create a single vector that replicates each element in the first column the number of times appearing in the second column.
>
> For example, I have the following matrix:
>
> 1 3
> 2 2
> 3 2
> 3 3
> 4 1
> 5 1
>
> And I want it to appear as follows:
>
> 1
> 1
> 1
> 2
> 2
> 3
> 3
> 3
> 3
> 3
> 4
> 5
>
> Can anyone provide help doing this?
>
> Thanks!

this FEX submission will do what you want

http://www.mathworks.com/matlabcentral/fileexchange/6436

% eg, if your data is in mat v

r=rude(v(:,2),v(:,1))
% r = 1 1 1 2 2 3 3 3 3 3 4 5

us
From: Matt Fig on 17 Jun 2010 15:49
Just to be a stinker, I'll give a vectorized approach:

% Data
A = [1.3 3;2.2 2;3 2;3 3;4.5 1;5 1;6 0;-4 2];


% Engine
nz = A(:,2)~=0;
idx = A(nz,1);
CS = cumsum(A(nz,2));
y = zeros(CS(end),1);
y([1; CS(1:end-1)+1]) = 1;
y = idx(cumsum(y))
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