how to find a pattern repetition in rows of a matrix

Hi,

I have a matrix similar to this:

A=  [1     0     2     0;
     2     1     0     1;
     0     0     2     0;
     2     1     1     1];

First I would like to select specific rows according to the last column of the matrix, for example, I would like to select the rows corresponding to the 0 value of the last column, in this case, are the first and third rows:

B=[  1     0     2 ;
     0     0     2  ]

Now I would like to see if in the rows of B a number in a certain position is repeated, in this case, 0 2 is the pattern repeated in the selected rows.

I obtained as output a matrix like this:

C=[2  3;
   0  2]

where the first row contains the position of the elements repeated in B, and in the second row the corresponding value.

Until now I have this code: ind = find(A(:,end)==1); res = A(ind,1:end-1); for i=1:4 yes(i)=all(~diff(res(:,i))); end lab=find(yes); val=res(1,yes); out=[lab; val];

there is a more efficient way? thanks

Answer 1

[Image Analyst]

Is this homework? (Sounds like it)

Try this:

A=  [1     0     2     0;
  2     1     0     1;
  0     0     2     0;
  2     1     1     1];

rowsToExtract = A(:,end) == 0
B = A(rowsToExtract, 1:end-1)

For C, I'll give a hint of trying to use strfind() or ismember().