Calculating the distance matrix from coordiante matrix

Hello,

How can I calculate the distance matrix? for example I have the coordinate matrix: A=[3 5 4 5; 1 2 6 3] and I want to find the distance between each pair of points.

Thanks in advance for any help!

Answer 1

[Kelly Kearney]

If you have the Stats Toolbox, pdist, as already mentioned:

A=[3 5 4 5; 1 2 6 3] 
squareform(pdist(A'))

ans =

            0       2.2361        5.099       2.8284
       2.2361            0       4.1231            1
        5.099       4.1231            0       3.1623
       2.8284            1       3.1623            0

If you don't have the Stats Toolbox, you can calculate the distance manually:

dx = bsxfun(@minus, A(1,:), A(1,:)');
dy = bsxfun(@minus, A(2,:), A(2,:)');
sqrt(dx.^2 + dy.^2)

ans =

            0       2.2361        5.099       2.8284
       2.2361            0       4.1231            1
        5.099       4.1231            0       3.1623
       2.8284            1       3.1623            0

[Nour BS]

Thank you everyone!

Answer 2

[Walter Roberson]

pdist() if you have the stats toolbox

[Nour BS]

Actually I want to have the "matrix distance" of these points above...

[Walter Roberson]

What is "matrix distance" of points?

http://www.mathworks.com/help/stats/pdist.html

pdist allows you to pass any of several different distance function names as a string in the second parameter, or you can pass a custom distance function by function handle.

[Nour BS]

d=Boxdist(A) ==> d =

     0     2     5     2
     2     0     4     1
     5     4     0     3
     2     1     3     0

But this result is not exact... I must find: d =

     0          2.2361     5.099      2.8284
     2.2361     0          4.1231     1
     5.099      4.1231     0          3.1623
     2.8284     1          3.1623          0