How to Speed up code

Hi, I have this code: I have a number of user and for all of them I want to find the id of locations that they have visited, the stay time and, combining this elements,the semantic trajectories associated to them

for userid=1:usercount
      % identification locationId: the location id are in a struct s.loc_ids
      for i=1:size(Trajectories(1,userid).label,1) 
          Trajectories(1,userid).locationId(i,1)=s(1,k).loc_ids(i,1); 
      end 
      for i=1:size(Trajectories(1,userid).label,1)-1
        % stayTime (difference between time of arrival and time of exit from a cell) for every user
          Trajectories(1,userid).stayTime(i,:)=abs((Trajectories(1,userid).dateAll(i+1,:)-Trajectories(1,userid).dateAll(i,:))); 
        % stayLocation for every user
          Trajectories(1,userid).stayLocation(i,:)=[Trajectories(1,userid).locationId(i,1) Trajectories(1,userid).dateAll(i+1,:) Trajectories(1,userid).stayTime(i,:)]; 
        % semantic trajectories for every user
          Trajectories(1,userid).semanticTraj(i,:)=[Trajectories(1,userid).stayLocation(i,:) Trajectories(1,userid).label(i,:)];  
      end
end

It run and do what I want but It's slow: can you help me to obtain better performance?

Answer 1

[Jan]

for userid = 1:usercount
  T = Trajectories(1, userid);  % Nicer code...
  n = size(T.label,1);
  T.locationId(1:n) = s(1,k).loc_ids(1:n);
  % Or perhaps:
  % T.locationId = s(1,k).loc_ids;
  T.stayTime = abs(diff(T.dateAll - T.dateAll, 1, 1)); 
  T.stayLocation = [T.locationId(1:n-1), T.dateAll(2:n, :), T.stayTime(1:n-1, :)]; 
  T.semanticTraj = [T.stayLocation(1:n-1,:), T.label(1:n-1, :)];
  Trajectories(1, userid) = T;
end

Without your data, I cannot debug this. Perhaps you need some .' operators for transposing.