# In two processed images, one shows 3 centroids and another shows 4 centroids. How to eliminate this extra centroids from centroids array.

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Naseeb Gill on 24 Feb 2016
Commented: Naseeb Gill on 1 Mar 2016
I have two images taken from two stereo cameras in which one contain three white objects and another contain four white objects. I processed both images to find out the centroids. Ofcourse first one give three centroids and second give four centroids and I stored these centroids into arrays called 'centroids1' and 'centroids2'. Now, I want two things here. First, if in 'centroids1' first entry is for object 1, then in 'centroids2' also, first entry should be for object 1 only, likewise for all objects. Second, I want to eliminate any extra centroids present in any of 'centroids' array i.e. I want only corresponding centriods in both 'centroids1' and 'centroids2' array.
I'm attaching my images and code here.

Dima Lisin on 29 Feb 2016
Hi Naseeb,
The triangulate function can return reprojection errors, which can tell you whether or not a match is correct.
Naseeb Gill on 1 Mar 2016
Thanks Dima, As you suggest triangulate function, using this clue I tried to solve my problem and I came out with this code. It works similar to as I want.
B = centroids1; % center of white objects from left cam
A = centroids2; % center of white objects from right cam
n = size(A,1);
m = size(B,1);
s = n-m;
if s >= 0
A(m+1:n,:)=[];
else
B(n+1:m,:)=[];
end
r = reprojectionErrors; % obtain from triangulate function
C = cat(2,B,r(:,1)); % for left image
D = cat(2,A,r(:,1)); % for right image
nA=[];
for j=1:size(C,1)
if (C(j,3)<3);
nA=[nA; C(j,:)];
end
end
nB=[];
for j=1:size(D,1)
if (D(j,3)<3);
nB=[nB; D(j,:)];
end
end
Suggest something if I missed or can be add in this. Also, I'm using triangulate function to find center of white objects,so suggest something regarding how to approach effectively please.
Thanks.

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