how to calculate the distances between pairwise coordinates using loops? Please help me...

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Hi,
I have a 4x6 matrix(A).
A= [50 56 76 55 63 63;
51 60 77 55 63 62;
51 60 77 55 64 64;
51 59 75 55 62 63]
Matrix A was formed as:
A=[X1 Y1 X2 Y2 X3 Y3]
or A=[point1 point2 point3] % point1 is (X1,Y1), point2(X2,Y2),
first column is keeping the x-coordinate...etc.
I have 4 observations(rows) and each observation has 3 points(6 columns). I want to calculate the eucledian distance and create a new matrix which is holding the all possible distances for each observation.
for example; distances for observation 1:
distance1=sqrt((X1-X2)^2 + (Y1-Y2)^2), %distance between point1 and point2
distance2=sqrt((X1-X3)^2 + (Y1-Y3)^2), %distance between point1 and point3
distance3=sqrt((X2-X1)^2 + (Y2-Y1)^2), %distance between point2 and point1
distance4=sqrt((X2-X3)^2 + (Y2-Y3)^2), %distance between point2 and point3
distance5=sqrt((X3-X1)^2 + (Y3-Y1)^2), %distance between point3 and point1
distance6=sqrt((X3-X2)^2 + (Y3-Y2)^2), %distance between point3 and point2 and
also repetitive distance is not important
I want to use any loop to creat my distances matrix which is shown below
distancesMatrix=[distance1 distance2 distance3 distance4 distance5 distance6]; % 4x6 matrix
could you please help me?
thanks in advance..

Accepted Answer

John BG
John BG on 2 Apr 2016
Edited: Stephen23 on 25 Feb 2018
Yavuz
In this question you have only 3 points, but you may need more.
The function combinator.m is really useful when the amount of points increases, copy of combinator.m following these lines.
You mention in your question that you need the combinations with repetition. With 3 points makes 6:
combinator(3,2,'p')
=
2 1
1 2
3 1
1 3
3 2
2 3
However, since you are calculating distances you don't really need to calculate 6 distances, but just 3, because distance 1-2 is same as 2-1 and so on, then you need:
combinator(3,2,'c')
=
1 2
1 3
2 3
The answer starts here:
amount_points=3
amount_dist=numel(combinator(amount_points,2,'c'))/2 % how many distances to calculate for each round
[szA1 szA2]=size(A)
amount_observations=szA1 % how many rounds
distance=zeros(amount_observations,amount_dist) % make room for result
pair=combinator(amount_dist,2,'c') % all point pairs
for k=1:amount_observations
for j=1:amount_dist
distance(k,j)=(A(k,pair(j,1)).^2+A(k,pair(j,2)).^2).^.5
end
end
If you find this answer of any help solving your question, please click on the thumbs-up vote link,
thanks in advance
John
EDIT: copyright code removed

More Answers (1)

Sanaz Kb
Sanaz Kb on 23 Feb 2018
Edited: Sanaz Kb on 23 Feb 2018
Hello,
I have the same question. but instead of relating one-by-one points,I should relate all points with one reference point. could you pleas help me?
Another question: i implement your function code in my Matlab but it doesn't work. (It get me an error message in this line- error('Only 2, 3 or 4 inputs are allowed. See help.')-
Thanks
  6 Comments
Sanaz Kb
Sanaz Kb on 25 Feb 2018
https://nl.mathworks.com/matlabcentral/answers/384700-how-to-calculate-the-distances-between-points-coordinates-and-the-arbitrary-reference-point-using-lo

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