Measuring distance using "pdist()"

Hi, I am relatively new to Matlab, and I have a question regarding the function pdist(), I have a following code:

 %      RA        Dec
 A = [00 08.2  +29 04   
      12 54.0  +56 00
      12 55.4  +3 25
      17 58.8  -9 46
      18 05.6  -30 25
      23 03.7   +28 04
      23 04.6   +15 11
      23 39.3   +77 36];
      Ar = [A(:,1)+A(:,2)/60 A(:,3)+A(:,4)/60];
      [X,Y,Z] = sphere;                                                          
      [RAx,DCy,Zz] = sph2cart((Ar(:,1)*2*pi), Ar(:,2)*pi/180, ones(size(Ar,1)));
      figure(1)
      hm = mesh(X,Y,Z);
      hold on
      plot3(RAx, DCy, Zz, 'h', 'MarkerSize',5, 'MarkerFaceColor','b')
      hold off
      axis equal off
      set(hm, 'EdgeColor', 'k', 'FaceAlpha',0.5)
      view(55,20)
      distance = pdist(Ar,'euclidean');
      Z = squareform(distance);

basically A is the right ascension and declination of a particular star, and I used the pdist(Ar,'euclidean') to obtain the distance between any 2 points.

The question is: Does the distance obtained by "pdist" equal to the distance between 2 points on a sphere or is it on a 2D plane?

Answer 1

[Walter Roberson]

You are taking Euclidean distance between two vectors (with assumed magnitude). You should probably be taking arccos of the dot product. https://www.wikihow.com/Find-the-Angle-Between-Two-Vectors