MATLAB Central Newsreader - how to copy a submatrix fro ma matrix

how to copy a submatrix fro ma matrix

Kishore — Tue, 03 Nov 2009 23:36:05 -0500

hello,

I would want to know if there is any command by which i can copy a sub matrix from a matrix.
What i mean is ,

A = [ 1 2 3 4 5 6;
          3 4 4 5 6 7;
          1.0e-2 1.2e-2 1.3e-2...
          1 2 3 4 5 5]

In the above matrix, i need to copy all elements which are greater than 1,to some matrix,( i.e i do no want the row 1.0e-2.....

This can ofcourse be done in a loop,but is there any command which simplifies the process?

I used bsxfun() ,but it doesnt seem to have this feature.

Thanks

Re: how to copy a submatrix fro ma matrix

ade77 — Wed, 04 Nov 2009 00:03:04 -0500

type doc find. or help find.
the 'find' function will return the indicies of the elements or rows that meet your conditions.
Then pass the indicies back to your sub array.
"Kishore " <kishore3385@yahoo.co.in> wrote in message <hcqep5$f8g$1@fred.mathworks.com>...
> hello,
>
> I would want to know if there is any command by which i can copy a sub matrix from a matrix.
> What i mean is ,
>
> A = [ 1 2 3 4 5 6;
> 3 4 4 5 6 7;
> 1.0e-2 1.2e-2 1.3e-2...
> 1 2 3 4 5 5]
>
> In the above matrix, i need to copy all elements which are greater than 1,to some matrix,( i.e i do no want the row 1.0e-2.....
>
> This can ofcourse be done in a loop,but is there any command which simplifies the process?
>
> I used bsxfun() ,but it doesnt seem to have this feature.
>
>
> Thanks

Re: how to copy a submatrix fro ma matrix

dpb — Wed, 04 Nov 2009 00:23:59 -0500

ade77 wrote:
...[top posting repaired...please don't do that]...
> "Kishore " <kishore3385@yahoo.co.in> wrote in message <hcqep5$f8g$1@fred.mathworks.com>...
...
>> I would want to know if there is any command by which i can copy a
>> sub matrix from a matrix.
...
>>
>> In the above matrix, i need to copy all elements which are greater
>> than 1,to some matrix,( i.e i do no want the row 1.0e-2.....
>>
>> This can ofcourse be done in a loop,but is there any command
>> which simplifies the process? >>
>> I used bsxfun() ,but it doesnt seem to have this feature.
>>
...
> type doc find. or help find.
> the 'find' function will return the indicies of the elements or rows
> that meet your conditions.
> Then pass the indicies back to your sub array.

Better yet, look up and read about

"logical addressing"

B=A(A>1);

Note however, your example matrix and your description of what you want
aren't quite consonant--saving the elements >1 will eliminate at least a
couple of entries in A that are identically one, not just the row w/
values <1.

If that's what you want precisely, for the sample A you would need

B=A(A>=1);

Also note that there will be a question to decide on what the shape of
the resultant will be--the above will return a column vector which you
can reshape() as desired if necessary.

--

Re: how to copy a submatrix fro ma matrix

ImageAnalyst — Wed, 04 Nov 2009 03:25:08 -0500

Here's a variant on what the others offered. Like they said, your
request is somewhat ambigous.

A = [ 1 2 3 4 5 6; ...
       3 4 4 5 6 7; ...
       1.0e-2 1.2e-2 1.3e-2 1.0e-2 1.2e-2 1.3e-2;...
       1 2 3 4 5 5]
B = zeros(size(A))
keeperIndexes = A>1
B(keeperIndexes) = A(keeperIndexes)

Re: how to copy a submatrix fro ma matrix

dpb — Wed, 04 Nov 2009 15:06:39 -0500

ImageAnalyst wrote:
> Here's a variant on what the others offered. ...

or yet another...

> A(A<1)=[]
A =
1 3 4 2 4 4
>

:)

--

Re: how to copy a submatrix fro ma matrix

Kishore — Thu, 05 Nov 2009 02:52:02 -0500

thanks everybody...