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Re: Easy about Matrices
From: |
Peter Bodin |
Subject: |
Re: Easy about Matrices |
Date: |
Tue, 19 Apr 2005 11:22:53 +0200 (CEST) |
User-agent: |
SquirrelMail/1.4.4-2 |
> On Mon, 18 Apr 2005, Quentin Spencer wrote:
>
>> I'm not completely sure if this is what you're looking for, but
>> maybe
>> this example helps:
>>
>> x = randn(1,1000);
>> x_positive = x(find(x>=0));
>> x_negative = x(find(x<0));
>
>
> That seems like it must have been an excellent answer for Alvaro. I
> have
> a related question. Suppose I have a vector like this:
>
> X=[1, 3, 9, 2, 4, 2, 7, 5, 3, 2, 9, 7]';
>
> And suppose I want the indices of all elements of X that are in this
> vector Y:
>
> Y=[2, 3, 9]';
>
> I can see how to do it with a loop...
>
> index=find(X==Y(1)); for i=2:length(Y), index=[index ;
> find(X==Y(i))]; end
>
> ...but can it be done without a loop? (Also, my method is a little
> awkward and I wouldn't mind hearing about how I could do it better.)
>
> Mike
>
>
>
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>
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> -------------------------------------------------------------
>
>
How about
>> find(ismember(X,Y))
ans =
2
3
4
6
9
10
11
provided that you have the functions from octave-forge.
HTH
PB
-------------------------------------------------------------
Octave is freely available under the terms of the GNU GPL.
Octave's home on the web: http://www.octave.org
How to fund new projects: http://www.octave.org/funding.html
Subscription information: http://www.octave.org/archive.html
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- Re: Easy about Matrices, (continued)
- Re: Easy about Matrices, avraham, 2005/04/18
- Re: Easy about Matrices, Mike Miller, 2005/04/18
- Re: Easy about Matrices, Geordie McBain, 2005/04/18
- Re: Easy about Matrices, Mike Miller, 2005/04/18
- Re: Easy about Matrices, Alvaro Aguilera, 2005/04/19
- Re: Easy about Matrices,
Peter Bodin <=
- Re: Easy about Matrices, Alvaro Aguilera, 2005/04/19
- Re: Easy about Matrices, Peter Bodin, 2005/04/19
- Re: Easy about Matrices, Mike Miller, 2005/04/19
- FW: Easy about Matrices, Frank Palazzolo, 2005/04/18