MATLAB Central Newsreader - Match matrix elements

Match matrix elements

Bobba Marco — Tue, 20 Jan 2009 12:09:03 -0500

Hi, I have two matrix A and B:

A = 43000000 x 5
B = 1 x 5

I show an example to clarify the target:

A = [11 22 34 56 89 B = [11 66 44 40 90}
       23 44 11 20 66
       79 54 32 17 89
       11 66 21 45 90
        ... ... ... ... ...]

RESULTS = [1 0 0 0 0
                  0 1 1 0 1
                  0 0 0 0 0
                  1 1 0 0 1
                  .. .. .. .. ..]

I would like to build a matrix (RESULTS) in which appears 1 if an element of B is present in A and zero if not present.
I used "ismember" function but the error HELP OF MEMORY appears.

Can you help me to solve problems in a short time?

Thanks

Marco

Re: Match matrix elements

Bruno Eklund — Tue, 20 Jan 2009 13:29:02 -0500

"Bobba Marco" <bobbaNO@mfn.SPAM.unipmn.it> wrote in message <gl4esv$t3e$1@fred.mathworks.com>...
> Hi, I have two matrix A and B:
>
> A = 43000000 x 5
> B = 1 x 5
>
> I show an example to clarify the target:
>
> A = [11 22 34 56 89 B = [11 66 44 40 90}
> 23 44 11 20 66
> 79 54 32 17 89
> 11 66 21 45 90
> ... ... ... ... ...]
>
> RESULTS = [1 0 0 0 0
> 0 1 1 0 1
> 0 0 0 0 0
> 1 1 0 0 1
> .. .. .. .. ..]
>
> I would like to build a matrix (RESULTS) in which appears 1 if an element of B is present in A and zero if not present.
> I used "ismember" function but the error HELP OF MEMORY appears.
>
> Can you help me to solve problems in a short time?
>
> Thanks
>
> Marco

Hi Marco,
try this:

RESULTS = zeros(size(A));
for i = 1: size(B,2)
RESULTS = RESULTS + ( A == B(1,i) );
end

That should work, even though you have to loop over all
the elements in B. Might be possible some more general
matrix methods exist, but I havn't found any in my work.

Good luck,
Bruno Eklund

Re: Match matrix elements

Roger Stafford — Tue, 20 Jan 2009 15:50:18 -0500

"Bobba Marco" <bobbaNO@mfn.SPAM.unipmn.it> wrote in message <gl4esv$t3e$1@fred.mathworks.com>...
> Hi, I have two matrix A and B:
>
> A = 43000000 x 5
> B = 1 x 5
>
> I show an example to clarify the target:
>
> A = [11 22 34 56 89 B = [11 66 44 40 90}
> 23 44 11 20 66
> 79 54 32 17 89
> 11 66 21 45 90
> ... ... ... ... ...]
>
> RESULTS = [1 0 0 0 0
> 0 1 1 0 1
> 0 0 0 0 0
> 1 1 0 0 1
> .. .. .. .. ..]
>
> I would like to build a matrix (RESULTS) in which appears 1 if an element of B is present in A and zero if not present.
> I used "ismember" function but the error HELP OF MEMORY appears.
>
> Can you help me to solve problems in a short time?
>
> Thanks
>
> Marco

I wouldn't be surprised if you are running out of memory, Marco. If you are using 'double' in A, it is filling up 43000000 x 5 x 8 = 1.72 gigabytes of contiguous memory. Creating room for 'RESULTS' will add substantially to this total. The 'ismember' function is the correct one to be using, but it also will need great quantities of memory to carry out its task in this case. You may be forced to work with smaller-sized matrices. The limitation is not matlab but the available resources on your computer.

Roger Stafford

Re: Match matrix elements

Loren Shure — Tue, 20 Jan 2009 16:16:01 -0500

In article <gl4esv$t3e$1@fred.mathworks.com>, bobbaNO@mfn.SPAM.unipmn.it
says...
> Hi, I have two matrix A and B:
>
> A = 43000000 x 5
> B = 1 x 5
>
> I show an example to clarify the target:
>
> A = [11 22 34 56 89 B = [11 66 44 40 90}
> 23 44 11 20 66
> 79 54 32 17 89
> 11 66 21 45 90
> ... ... ... ... ...]
>
> RESULTS = [1 0 0 0 0
> 0 1 1 0 1
> 0 0 0 0 0
> 1 1 0 0 1
> .. .. .. .. ..]
>
> I would like to build a matrix (RESULTS) in which appears 1 if an element of B is present in A and zero if not present.
> I used "ismember" function but the error HELP OF MEMORY appears.
>
> Can you help me to solve problems in a short time?
>
> Thanks
>
> Marco
>
>

You inspired me to blog on this topic:
http://blogs.mathworks.com/loren/2009/01/20/more-ways-to-find-matching-
data/

The short answer is:

FinalAnswer = ismember(A,B)

will get you the results you are looking for.

--
Loren
http://blogs.mathworks.com/loren

Re: Match matrix elements

Jos — Wed, 21 Jan 2009 11:29:02 -0500

Loren Shure <loren@mathworks.com> wrote in message <MPG.23dfc2bb167363f998992c@news.mathworks.com>...
> In article <gl4esv$t3e$1@fred.mathworks.com>, bobbaNO@mfn.SPAM.unipmn.it
> says...
> > Hi, I have two matrix A and B:
> >
> > A = 43000000 x 5
> > B = 1 x 5
> >
> > I show an example to clarify the target:
> >
> > A = [11 22 34 56 89 B = [11 66 44 40 90}
> > 23 44 11 20 66
> > 79 54 32 17 89
> > 11 66 21 45 90
> > ... ... ... ... ...]
> >
> > RESULTS = [1 0 0 0 0
> > 0 1 1 0 1
> > 0 0 0 0 0
> > 1 1 0 0 1
> > .. .. .. .. ..]
> >
> > I would like to build a matrix (RESULTS) in which appears 1 if an element of B is present in A and zero if not present.
> > I used "ismember" function but the error HELP OF MEMORY appears.
> >
> > Can you help me to solve problems in a short time?
> >
> > Thanks
> >
> > Marco
> >
> >
>
> You inspired me to blog on this topic:
> http://blogs.mathworks.com/loren/2009/01/20/more-ways-to-find-matching-
> data/
>
> The short answer is:
>
> FinalAnswer = ismember(A,B)
>
> will get you the results you are looking for.
>
>
> --
> Loren
> http://blogs.mathworks.com/loren

Perhaps I have missed something but I assumed the problem was that the OP tried ISMEMBER but ran into memory issues?

Jos

Re: Match matrix elements

us — Wed, 21 Jan 2009 14:27:02 -0500

Loren Shure

> > bobbaNO@mfn.SPAM.unipmn.it
> > I would like to build a matrix (RESULTS) in which appears 1 if an element of B is present in A and zero if not present.
> > I used "ismember" function but the error HELP OF MEMORY appears.

> The short answer is:
> FinalAnswer = ismember(A,B)

that's exactly what the OP tried (the typical CSSM solution)... but he/she ran into memory problems...

us