# 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..

##### 0 Comments

### Accepted Answer

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
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
on 25 Feb 2018

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