Need help with finding distances in a matrix program
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I have an A matrix, in which I need to find the distances between the points. I have the formulas, but I need help to translate this into matlab.
Lets say that a is equal to:
A=
0 1 0 0 1 0
1 0 0 0 0 0
0 0 0 0 1 0
I have a program to create a new matrix called B,finding this points in which the first column is the number of point, the second column is the x coordinate of the point and the third column is the y coordinate. In this case will be:
B=
1 2 1
2 5 1
3 1 2
4 5 3
Here is the code for this program:
clear z
p=1;
[row,col] = size(A);
for i = 1:row
for j=1:col
if(A(i,j)>0)
z(p,:)=[j,i];
p=p+1;
end
end
end
B=[(1:p-1)',z] %B matrix 1 col is #of point, 2 col is xcoord,3 col is ycoord
I need to find the distances between these points, in this case will be dijx(x distance) and dijy (y distance). For this matrix these will be the distances(absolute value from one point to another point):
dijx=
0 3 1 3
3 0 4 0
1 4 0 4
3 0 4 0
dijy=
0 0 1 2
0 0 1 2
1 1 0 1
2 2 1 0
Can you help me to create a for loop code to find those distances? Thank you!!
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Andrei Bobrov
2014-1-25
编辑:Andrei Bobrov
2014-1-25
[r,c]=find(A');
dij = dist([r,c]'); % dist from Neural Network Toolbox
or
[r,c]=find(A');
dijx = bsxfun(@minus,r,r');
dijy = bsxfun(@minus,c,c');
dij = hypot(dijx,dijy);
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更多回答(1 个)
Image Analyst
2014-1-25
You can get B in two lines of code:
[rows, columns] = find(A)
B = [[1:length(rows)]', rows, columns]
Now I'm not sure what distances you are after are you wanting every distance from N points to the other N-1 points? So you'll have every possible pairing and N*(N-1) distance?
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