# finding duplicate number and adjacent row value

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Sobhan on 16 Sep 2012
Suppose I have a matrix of values
v = [1 4; 1 5; 2 4; 2 4; 2 5; 2 5; 3 4; 3 7]
in column one the numbers are consecutive but with repetition, how can I find only the first numbers and corresponidng number in the other column, put them in a new matrix (v')? The new matrix should be like this from my example:
v'= [1 4; 2 4; 3 4]
I hope I am clear enough
Cheers
Sobhan

#### 1 Comment

Azzi Abdelmalek on 16 Sep 2012
what if v= [1 4; 1 5; 2 4; 2 4; 2 5; 2 5; 3 4; 3 7;1 5;1 6]?

Azzi Abdelmalek on 16 Sep 2012
v = [1 4; 1 5; 2 4; 2 4; 2 5; 2 5; 3 4; 3 7]
idx=diff(v(:,1))
v1=[];
if idx(1)==0
v1=[v1;v(1,:)]
end
for k=2:length(idx)
if idx(k)==0 & idx(k-1)~=0
v1=[v1; v(k,:)]
end
end

#### 1 Comment

Sobhan on 16 Sep 2012
Dear Azzi, your solution worked perfectly! Thanks a lot. Wayne`s method gave an error. Anyhow, thanks a lot to both of you

Wayne King on 16 Sep 2012
Edited: Wayne King on 16 Sep 2012
[~,iv] = unique(v(:,1),'stable');
vnew = v(iv,:);