MATLAB: How is the correct way to calculate distance of each data points between two vectors

Question

Hi, I would like to compute distance between two vectors. However, the result does not yields the expected outcome. First code:

X = rand(3,2)
D0 = pdist(X)
D1 = pdist(X,'minkowski')
X =
    0.8147    0.9134
    0.9058    0.6324
    0.1270    0.0975
D1 =
      0.2954    1.0670    0.9448

If i generate the random 3×2 data, the output yields as expectation. However, if i'm using the same function on the vectors, the result appears in the weird way as below Second code::

X1 = [4,10,1,1,2,7,12,5,6,10];
X2 = [3,9,7,8,2,7,12,5,1,3];
X = [X1;X2]'

output:

X =
       4     3
      10     9
       1     7
       1     8
       2     2
       7     7
      12    12
       5     5
       6     1
      10     3
D1 =
    Columns 1 through 10
      8.4853    5.0000    5.8310    2.2361    5.0000   12.0416    2.2361    2.8284    6.0000    9.2195
    Columns 11 through 20
      9.0554   10.6301    3.6056    3.6056    6.4031    8.9443    6.0000    1.0000    5.0990    6.0000
    Columns 21 through 30
     12.0830    4.4721    7.8102    9.8489    6.0828    6.0828   11.7047    5.0000    8.6023   10.2956
    Columns 31 through 40
      7.0711   14.1421    4.2426    4.1231    8.0623    7.0711    2.8284    6.0828    5.0000    9.8995
    Columns 41 through 45
     12.5300    9.2195    4.1231    5.3852    4.4721

I do wonder, why do the results must be 45 points of distance. By right, the result is supposed to produce 11 points of distance because my purpose it to compute the distance of each data points in vector 1 and vector 2 and i also just have 11 data points in vector 1 and vector 2. Appreciate if anyone could advice me to improve my code. Thanks

Answer 1

Hi,your Pairwise distance type calculate:

this code can help you

    clc
    clear
    X = rand(3,2);
    D1 = length(X(:,1)-X(:,2));