3D scatter plot with different color and legend explaining each color.

Hi,I want to draw a 3D scatter plot with different colors and want to put a legend that explains what each color means.

My example is something like this.

b's are the data points that I want to put in the 3D scatter. b1=[1,2,3,4,5] b2=[2,2,3,3,1] b3=[1,5,4,4,3]

s is the size of the points s=[1,1,1,1,1]

r is the color of the points (three colors) r=[0,0,2,1,2]

Finally the scatter plot is this = scatter3(b1,b2,b3,s,r,'filled')

My questions are. 1)Can I set a designate color to each numbers in r? for example, red for 0, blue for 1, green for 2. if so, How can I do it?

2) how can I set a legend that explains what the color means? for example. for color 0 - 'efficient', for color 1 - 'inefficient', for color 2- 'not an eq'

Answer 1

[Chad Greene]

Try this:

    b1=[1,2,3,4,5];
    b2=[2,2,3,3,1];
    b3=[1,5,4,4,3];
    s=[1,1,1,1,1];
    r=[0,0,2,1,2];
    scatter3(b1,b2,b3,s*50,r,'filled')

    % Define rgb colors manually: 
    colors = [1 0 0; % red
              0 0 1; % blue    
              0 1 0];% green

    colormap(colors);       
    cb = colorbar; 
    caxis([-0.5 2.5])
    set(cb,'ytick',0:2,'yticklabel',{'efficient','inefficient','not an eq'})

I had to increase the size of the points (multiplied by 50) because otherwise they're too small to see.

[Jinsoo Bae]

Okay. I understand the color, you mean this [1 0 0; 0 0 1; 0 1 0]? But my question is, how to put a designate color to each numbers in r. So here in the example, I want to have [red,red,green,blue,green]. Can I do this?

[Jinsoo Bae]

I found how to use the color mapping. Thank you. For who may look at this, refer to this question and answer. Why couldn't I find this before...

https://www.mathworks.com/matlabcentral/answers/225193-grouping-data-for-a-3d-scatter-plot

[Chad Greene]

Alternatively, you could use plot3 and plot each category of data separately like this:

b1=[1,2,3,4,5];
b2=[2,2,3,3,1];
b3=[1,5,4,4,3];
s=[1,1,1,1,1];
r=[0,0,2,1,2];

% get unique values of r:
ur = unique(r);    

% Define rgb colors manually: 
colors = [1 0 0; % red
          0 0 1; % blue    
          0 1 0];% green
hold on; 
view(3); 
grid on
for k = 1:3
   ind = r==ur(k); % indices corresponding to r=k
   plot3(b1(ind),b2(ind),b3(ind),'.','markersize',30,'color',colors(k,:))
end
legend('efficient','inefficient','not an eq')

[Mariia Iurkova]

Thank you, this solution helped my problem :)