substitution of values if is verified a condition

Hi,

I have a series of touristic trajectories in userTouristicTraj.touristicData.touristicTraj2 (attached); I want compare every pairs of coordinates in the array with the values in the first two columns of Clusters (attached): if there is a corrispondence, I want create a new array that instead the coordinates have the corresponding value in the 4 column of Clusters.

Example

userTouristicTraj(1).touristicData(1).touristicTraj2

ans =

     38.1153   13.3781
     38.1190   13.3742

I search this pairs

(38.1153 13.3781) (38.1190 13.3742)

in Clusters(:,1:2); if I find (38.1153 13.3781), put in userTouristicTraj(1).touristicData(1).traj the corrispondent value in Clusters(:,4) so

userTouristicTraj(1).touristicData(1).traj = (1; 1)

I want to do this for all the values in userTouristicTraj.touristicData.touristicTraj2. Can you help me? I hope the question is clear

Answer 1

[Guillaume]

This should work:

for userTouristicTrajidx = 1:numel(userTouristicTraj)
  for touristicDataidx = 1:numel(userTouristicTraj(userTouristicTrajidx).touristicData)
      touristicTraj = userTouristicTraj(userTouristicTrajidx).touristicData(touristicDataidx).touristicTraj2;
      traj = nan(size(touristicTraj, 1), 1);
      if ~isempty(touristicTraj)
         [found, whichrow] = ismember(touristicTraj, Clusters(:, [1, 2]), 'rows');
         traj(found) = Clusters(whichrow(found), 4); 
      end
      userTouristicTraj(userTouristicTrajidx).touristicData(touristicDataidx).traj = traj;
   end
end

Note: This is using ismember which means that the numbers must be exactly identical*. If the numbers in touristicTraj2 and Clusters were obtained from different calculations, then it is very likely they won't be exactly the same (e.g. 0.1+0.1+0.1 is not the same as 0.3). If that is the case, then use ismembertol instead. ismembertol is significantly slower than ismember.

Note 2: I don't know how you generated your touristicTraj2 fields but some of them are empty with size (0, 0). It would have been much better to create them empty with size (0, 2). While for most purpose both are the same (just empty arrays), it matters for ismember. Using the latter empty would have avoided the if ~isempty(touristicTraj) test.

Note 3: You haven't specified what to write when no match is found. I've put NaN. Replace as appropriate.