How to give different colors to different tracts?

Hi.

I have some tracts and i can plot them using plot3. I would like to give to each tract a color, using some information about the relative distance between the first and last point of that tract.

For example: Tract1 goes from (1,1,1) to (6,8,12). So: Diff is (5,7,11).

I know that RGB codes are something like [1 0 0] or [1 0.4 0.6]. With this i made [(Diff(1)/(Diff(1)+Diff(2)+Diff(3)) (Diff(2)...) (Diff(3)...)] but it gives me this error: 'Error in color/linetype argument'.

How can i solve this?

Thanks in advance

[Gustavo]

I found it. If anyone needs it there it is:

function []= Test (TRACTS%%Cell with structs within, INFO%Information about each tract)

   close all; 
   for i=1:INFO.n_count 
       clear V; 
       for j=1:size(TRACTS{i}) 

       G(j) = TRACTS{i}(j,1); %Info about x axis 
       H(j) = TRACTS{i}(j,2); %Info about y axis
       I(j) = TRACTS{i}(j,3); %Info about z axis    

       J = G(j)-G(1); 
       K = H(j)-H(1); 
       L = I(j)-I(1); 

       V(j,1)=J; 
       V(j,2)=K;
       V(j,3)=L;       

       W(i,j) = abs(V(j,1))+abs(V(j,2))+abs(V(j,3));       

       end   

       %knowing that RGB color codes are [a b c]
       %we consider the weight that each V has in the W
       %obtaining something like [0.1 0.2 0.6]
       M = [abs(V(j,1))/W(i,j) abs(V(j,2))/W(i,j) abs(V(j,3))/W(i,j)];

      plot3(TRACTS{i}(:,1),TRACTS{i}(:,2),TRACTS{i}(:,3),'Color',M);grid on;

   hold on;

   end

end

[the cyclist]

You could put this as an answer (rather than a comment), and accept it.

[Jan]

j=1:size(TRACTS{i}) is at least confusing: size() replies a vector and what do you expect as output of: 1:[22,23]? So better define the wanted dimension in the size() command.

There is no reason to clear 'V'. A pre-allocation would be much more important instead:

V = zeros(size(TRACTS{i}, 1), 3);

Answer 1

[Gustavo]

By sugestion of the cyclist:

I found it. If anyone needs it there it is:

function []= Test (TRACTS%%Cell with structs within, INFO%Information about each tract)

   close all; 
   for i=1:INFO.n_count 
       clear V; 
       for j=1:size(TRACTS{i}) 
       G(j) = TRACTS{i}(j,1); %Info about x axis 
       H(j) = TRACTS{i}(j,2); %Info about y axis
       I(j) = TRACTS{i}(j,3); %Info about z axis    
       J = G(j)-G(1); 
       K = H(j)-H(1); 
       L = I(j)-I(1); 
       V(j,1)=J; 
       V(j,2)=K;
       V(j,3)=L;       
       W(i,j) = abs(V(j,1))+abs(V(j,2))+abs(V(j,3));       
       end   
       %knowing that RGB color codes are [a b c]
       %we consider the weight that each V has in the W
       %obtaining something like [0.1 0.2 0.6]
       M = [abs(V(j,1))/W(i,j) abs(V(j,2))/W(i,j) abs(V(j,3))/W(i,j)];
      plot3(TRACTS{i}(:,1),TRACTS{i}(:,2),TRACTS{i}(:,3),'Color',M);grid on;
   hold on;
   end
end

I am not sure of what you pretended Jan Simon. I need to change the number of iterations for each position of the cell TRACTS, because the number of points used to generate a track differs. I made this code and he works reasonibly well. However i am open to any changes that you or anyone sugest in order to enhance this code :)