exstract consecutive duplicate element of array

Dear Dear I've got the folowing problem Given an A matrix nxm i need to exstract consecutive duplicate elements of array

so I mean if for excample the row n=n+1 =n+2 I want to get a matrix B obtainet from A less the rows duplicate

[madhan ravi]

Example of your output?

[ADC]

For exsamples the second coloumn the secon line have the value 2 duplicate

so the functions i need is to get te matrix B as following

A =
     1     2     3
     1     2     7
     3     4     9

K>> B=[1 2 3;3 4 9]

B =
     1     2     3
     3     4     9

[jonas]

I think you missed some ;'s there? Should it be

A = [1 2 3; 1 2 7; 3 4 9]

and the output

B = [1 2 3; 3 4 9]

?? I'm just guessing here

[ADC]

yess

Answer 1

[Stephen23]

>> A = [1,2,3;1,2,7;3,4,9;9,9,9;7,7,7]
A =
   1   2   3
   1   2   7
   3   4   9
   9   9   9
   7   7   7
>> B = A([true;all(diff(A,1,1)~=0,2)],:)
B =
   1   2   3
   3   4   9
   7   7   7

[Andrei Bobrov]

+1

Answer 2

[jonas]

A is your matrix. This line removes duplicates:

A([false diff(A)==0]) = [];

Or you could expand it to this, given your vague example from the comments

A =

     1     2     3
     1     2     7
     3     4     9

_

mask = [ones(1,size(A,1));diff(A,1)] == 0;
A = A(sum(mask,2)==0,:)

A =

     1     2     3
     3     4     9

[ADC]

this is exsactly what I need but I whant that this check is done only for example a given coulumn, for example the coloumn 3

[jonas]

Simple enough, just change this line

mask = [false;diff(A(:,3))==0]

or simply write it like this

 mask = [false;diff(A(:,3))==0]
 A = A(~mask,:)

The number, in this case 3, determines the column over which the check is made