Thread Subject: comparing columns each element

I have a cell array R=(4096,2). I need to compare each
element (in this case the elements are 4x4 matrices) in the
first column to each element in the 2nd. If a matrix in the
2nd column is the same as one in the first then i need to
change the matrix in the 2nd column to the zero matrix.
How can I do this? (I have tried creating a loop but it
only compares matrices that are in the same row.) I also
have them in seperate cell arrays. Would it be easier to
compare them that way?
thanks!

In article <g2r7ih$550$1@fred.mathworks.com>,
Katie <kmcdon03@uoguelph.ca> wrote:
>I have a cell array R=(4096,2). I need to compare each
>element (in this case the elements are 4x4 matrices) in the
>first column to each element in the 2nd. If a matrix in the
>2nd column is the same as one in the first then i need to
>change the matrix in the 2nd column to the zero matrix.
>How can I do this? (I have tried creating a loop but it
>only compares matrices that are in the same row.) I also
>have them in seperate cell arrays. Would it be easier to
>compare them that way?

I think this should work:

R(equal(R(:,1),R(:,2)),2) = {zeros(4,4)};

--
  "Not the fruit of experience, but experience itself, is the end."
                                              -- Walter Pater

> R(equal(R(:,1),R(:,2)),2) = {zeros(4,4)};

i tried this and it came up with this error message:

??? Undefined function or method 'equal' for input arguments
of type 'cell'.

thanks for the help!

In article <g2rq31$bgp$1@fred.mathworks.com>,
Katie <kmcdon03@uoguelph.ca> wrote:

>
>> R(equal(R(:,1),R(:,2)),2) = {zeros(4,4)};

>i tried this and it came up with this error message:

>??? Undefined function or method 'equal' for input arguments
>of type 'cell'.

Sorry, that should have been isequal() instead of equal()
--
  "The whole history of civilization is strewn with creeds and
  institutions which were invaluable at first, and deadly
  afterwards." -- Walter Bagehot

"Katie ":
<SNIP looking for equal contents

one of the many solutions

% the data
     m=1:3;
     c={
          m,m
          m,-m
          m,m
          m,-m
     };
% the engine
     ix=cellfun(@(x,y) isequal(x,y),c(:,1),c(:,2));
     c(ix,2)={0*m};
% the result
     cat(1,c{:,2})
%{
     only shows the contents of the col #2
     ans =
      0 0 0
     -1 -2 -3
      0 0 0
     -1 -2 -3
%}

us

thank you !

thank you!
could you send another one of the many solutions?
I am still not sure how to use that one.