Distance between points in a table

Hello all,

I have a table containing the (x,y) coordinates and I need to find the distance between each point and save it as an array. Could anybody please guide me?

Thanks in advance.

[Geoff Hayes]

K1495 - what can you tell us about your table? Can you convert it to an mx2 array for each of your m points? If you have the Statistics and Machine Learning Toolbox, you could probably use pdist.

[Adam Danz]

or pdist2

[KK14]

Hello,

I do not have access to the tool box. But anyways thanks for letting me know about 'pdist'.

BR

Answer 1

[Adam Danz]

>I have a table containing the (x,y) coordinates and I need to find the distance between each point [without using pdist | pdist2]

Calculate distances row-wise

Create input table

rng('default')
T = array2table(rand(8,2).*10, 'VariableNames',{'X','Y'})

T = 8x2 table
      X         Y   
    ______    ______

    8.1472    9.5751
    9.0579    9.6489
    1.2699    1.5761
    9.1338    9.7059
    6.3236    9.5717
    0.9754    4.8538
     2.785    8.0028
    5.4688    1.4189

Add a column Dist that shows the distance between rows n and n-1.

T.Dist = [NaN; sqrt(diff(T.X).^2 + diff(T.Y).^2)]

T = 8x3 table
      X         Y        Dist  
    ______    ______    _______

    8.1472    9.5751        NaN
    9.0579    9.6489    0.91367
    1.2699    1.5761     11.217
    9.1338    9.7059     11.311
    6.3236    9.5717     2.8134
    0.9754    4.8538     7.1317
     2.785    8.0028      3.632
    5.4688    1.4189     7.1099

Calculate pairwise distances

Create input table

rng('default')
T = array2table(rand(8,2).*10, 'VariableNames',{'X','Y'})

T = 8x2 table
      X         Y   
    ______    ______

    8.1472    9.5751
    9.0579    9.6489
    1.2699    1.5761
    9.1338    9.7059
    6.3236    9.5717
    0.9754    4.8538
     2.785    8.0028
    5.4688    1.4189

Create square matrix of pairwise distances

[xi, yi] = meshgrid(1:numel(T.X), 1:numel(T.Y));
D = reshape(sqrt(diff(T.X([xi(:),yi(:)]),1,2).^2 + diff(T.Y([xi(:),yi(:)]),1,2).^2),size(xi))

D = 8×8

0 0.9137 10.5490 0.9952 1.8236 8.5864 5.5880 8.5847 0.9137 0 11.2171 0.0949 2.7354 9.3979 6.4853 8.9786 10.5490 11.2171 0 11.3108 9.4588 3.2908 6.6029 4.2019 0.9952 0.0949 11.3108 0 2.8134 9.4922 6.5732 9.0613 1.8236 2.7354 9.4588 2.8134 0 7.1317 3.8708 8.1975 8.5864 9.3979 3.2908 9.4922 7.1317 0 3.6320 5.6559 5.5880 6.4853 6.6029 6.5732 3.8708 3.6320 0 7.1099 8.5847 8.9786 4.2019 9.0613 8.1975 5.6559 7.1099 0

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D(i,j) is the distance between points T(i,:) and T(j,:).