# Remove centroid locations of objects that are too close

조회 수: 1 (최근 30일)
Jason 2022년 8월 8일
댓글: Jason 2022년 8월 9일
Hi, I have a list of centroid locations of spots in an image (xf, yf). The spots are randomly distributed. I want to remove the centroid locations that are too close to each other, or say within a distance of d. I've got to the following but not sure what to do next. Also is there a better way to do this ratrher than use loops?
%using a loop
M=[];
for j=1:length(xf)
for i=1:length(xf)
dx=xf(j)-xf(i);
dy=yf(j)-yf(i);
dr=sqrt(power(dx,2)+power(dy,2));
M(j,1)=xf(j);
M(j,2)=yf(j);
M(j,3)=xf(i);
M(j,4)=yf(i);
M(j,5)=dr;
end
end
##### 댓글 수: 2없음 표시없음 숨기기
Matt J 2022년 8월 9일
If two spots are less than d apart should both be removed? If not, by what criterion do you decide which spot remains?
Image Analyst 2022년 8월 9일
To me it sounds like both are to be removed. This is easily done with pdist2.

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### 채택된 답변

Matt J 2022년 8월 9일
편집: Matt J 2022년 8월 9일
A=[xf(:) yf(:)];
D=pdist2(A,A);
D(D==0)=inf; %retroactive EDIT
keep = all(D>d,1);
xf=xf(keep);
yf=yf(keep);
##### 댓글 수: 7이전 댓글 5개 표시이전 댓글 5개 숨기기
Jason 2022년 8월 9일
Of course, its clear now, thankyou
Jason 2022년 8월 9일
Just to add, when I had over 400 objects, akthough i do other operations, using the for loop took 110s.using the pdist2 approach took just under 2s. Remarkable!

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### 추가 답변 (1개)

yanqi liu 2022년 8월 9일
yes，sir，may be use pdist2， such as
xf = rand(1, 10);
yf = rand(1, 10);
%using a loop
M=[];
for j=1:length(xf)
for i=1:length(xf)
dx=xf(j)-xf(i);
dy=yf(j)-yf(i);
dr=sqrt(power(dx,2)+power(dy,2));
M(end+1,1)=xf(j);
M(end,2)=yf(j);
M(end,3)=xf(i);
M(end,4)=yf(i);
M(end,5)=dr;
end
end
% second method
A=[xf(:) yf(:)];
B=pdist2(A,A);
C=B';
C=C(:);
isequal(M(:,end),C)
ans = logical
1

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