How to add different color for each galaxy

I am working on "Spiral Galaxy Formation Simulation" example in Mathworks. How can I add different colors for each galaxy's bodies? There is an option in each galaxy function for color but it doesn't work.

[Christos Dimopoulos]

I have bodies with 8 properties. Last one is color. In each galaxy's bodies I give the same color, but different than other galaxy bodies.

        bodies(i,8) = 'r';

When trying to plot seems I can't get it to color each body separately.

 for i = 1:n,
    points_x(i) = bodies(i,2);
    points_y(i) = bodies(i,3);
    points_z(i) = bodies(i,4);
    points_col(i) = bodies(i,8);
 end

 % Remove the old plot.
 if isempty(oldPlot)
    oldPlot = fig;

 elseif ~isempty(foundFig)
    delete(oldPlot);
 end

 oldPlot = plot3(points_x,points_y,points_z, points_col);
 drawnow

I get error: "An error occurred while running the simulation and the simulation was terminated Caused by: Not enough input arguments."

it only accepts one color for all

oldPlot = plot3(points_x,points_y,points_z, 'w.');

It might be the dot, I don't know...

Answer 1

[Image Analyst]

Use scatter3() instead of plot3() if you want to specify a color for each and every marker.

[Christos Dimopoulos]

Thanks. It seems that it could work, but when I put

 oldPlot = scatter3(points_x,points_y,points_z,points_size,points_col,'filled') ;

the color doesn't change. Probably because it is put with letter ('r') and not vector ( [0 1 1] ). Any ideas?

[Image Analyst]

points_col should be a 2-D array of length(points_x) rows and 3 columns instead of a single color like 'r'. If points_col is just 'r', then all points will be the same red color. If you want different colors, then pass in different colors in the array points_col.

[Christos Dimopoulos]

I would like the same color for each galaxy, this means 'r' for galaxy 1 (ex. bodies 1-250), 'w' for galaxy 2 (ex. bodies 251-500) etc. Do I still to do it with 2-D array?

[Image Analyst]

Yes, or if you want, you can just call scatter3 multiple times

scatter3(bodies(1:250), .... 'r',.....  % Call with red markers.
hold on;
scatter3(bodies(251:500), .... 'b',.....  % Call with blue markers.
scatter3(bodies(501:end), .... 'm',.....  % Call with magenta markers.

[Christos Dimopoulos]

Thanks again for the answer. The problem is that the number of bodies and galaxies, needs to change many times and I was hoping to have a way to do it automatically.

Also it doesn't seem to like the function

 if isempty(oldPlot)
    oldPlot = fig;

 elseif ~isempty(foundFig)
    delete(oldPlot);
 end

 oldPlot = scatter3(points_x(1:750),points_y(1:750),points_z(1:750),psize(1:750),'r','filled') ; 
 hold on;
 oldPlot = scatter3(points_x(751:1500),points_y(751:1500),points_z(751:1500),psize(751:1500),'w','filled') ;

because in the first scatter3 ('r') I get all particles positions and not the last ones, and seems like it is drawing trajectories.

[Image Analyst]

You can have the indexes be variables, like points_x(indexes(1):indexes(2)) etc.

I don't know why you're deleting the old plot. Why not simply call "cla reset" if you want to wipe everything clean?

[Christos Dimopoulos]

You are correct again!

cla fixed it!

cla reset unfortunately makes the axis appear from nowhere and loses its focus.

Anyway if it works with cla I am ok.