Add multiple legends to graph

I see a scatter plot that use different shapes of marker to indicate the source of data while using different color to indicate the area that each data point cover. I am able to produce the scatters but I don't know how to orgnize the legend like that.

If I use the default legend function in MatLab, it will give me all the combination of markers, which is lengthy.

Anyone know how to display the shape of marker and the color of marker seperately?

Answer 1

[Dave B]

You can't (easily) make multiple legends, but you can make a 'fake' legend by including some objects in your chart that have NaN data and telling legend to use those objects:

% Fake data: 3 colors by 3 markers, would be 9 legend items
scatter(randn(10,1),randn(10,1),'ro')
hold on
scatter(randn(10,1),randn(10,1),'bo')
scatter(randn(10,1),randn(10,1),'mo')
scatter(randn(10,1),randn(10,1),'r*')
scatter(randn(10,1),randn(10,1),'b*')
scatter(randn(10,1),randn(10,1),'m*')
scatter(randn(10,1),randn(10,1),'rs')
scatter(randn(10,1),randn(10,1),'bs')
scatter(randn(10,1),randn(10,1),'ms')

% Make some data just for legend:
hLeg = gobjects(6,1);
% I used a . marker for colors, maybe a good idea to use something not in
% your 'real' markers
hLeg(1) = scatter(nan,nan,'r.'); 
hLeg(2) = scatter(nan,nan,'b.');
hLeg(3) = scatter(nan,nan,'m.');
% Similarly I used black for markers
hLeg(4) = scatter(nan,nan,'ko'); 
hLeg(5) = scatter(nan,nan,'k*');
hLeg(6) = scatter(nan,nan,'ks');

legend(hLeg, 'red', 'blue', 'magenta', 'circle', 'asterisk', 'square')

[Dave B]

Similar approach with a mixed legend and colobrar:

scatter(randn(10,1),randn(10,1),40,randi(3,10,1),'o','filled')
hold on
scatter(randn(10,1),randn(10,1),40,randi(3,10,1),'*')
scatter(randn(10,1),randn(10,1),40,randi(3,10,1),'s','filled')
colormap(lines(3))

hLeg = gobjects(3,1);
hLeg(1) = scatter(nan,nan,'ko','filled');
hLeg(2) = scatter(nan,nan,'k*');
hLeg(3) = scatter(nan,nan,'ks','filled');
leg=legend(hLeg, 'circle', 'asterisk', 'square');

c=colorbar;
c.Ticks = [4/3 2 8/3];
c.TickLabels = ["color 1" "color 2" "color 3"];

[Hannah]

Thank you Dave! This is super helpful!

Haihui