Adding more circles to the scatter plot legend

I am using the following code and want to create a legend where different colors correspond to different dosage.

Currently, all the points are marked as the same color in the legend (attached)

dpli_dris = [1,2,3,4]
hub_dris = [1,2,3,3.5]
dosage_order = [1,2,3,4]
dosage = ['1 mcg/kg/min';'3 mcg/kg/min';'4 mcg/kg/min';'6 mcg/kg/min'];

handle = figure;
s=scatter(dpli_dris,hub_dris,[],'b','filled','o','MarkerEdgeColor',[0 0 0])
hold on
s.AlphaData = dosage_order;
s.MarkerFaceAlpha = 'flat';
leg = legend(dosage,'Location','northeastoutside');

What can I do to fix the legend?

Thank you

Answer 1

[VBBV]

If you want different colors, call the scatter function seperately for each point. Currently, you are assigning the same color blue to all the 4 points in vectors dpli_dris & hub_dris using single scatter call.

dpli_dris = [1,2,3,4];
hub_dris = [1,2,3,3.5];
dosage_order = [1,2,3,4];
dosage = {'1 mcg/kg/min','3 mcg/kg/min','4 mcg/kg/min','6 mcg/kg/min'};
hold on
scatter(dpli_dris(1),hub_dris(1),'b','filled','o','MarkerEdgeColor',[0 0 0])
scatter(dpli_dris(2),hub_dris(2),'r','filled','o','MarkerEdgeColor',[0 0 0])
scatter(dpli_dris(3),hub_dris(3),'g','filled','o','MarkerEdgeColor',[0 0 0])
scatter(dpli_dris(4),hub_dris(4),'m','filled','o','MarkerEdgeColor',[0 0 0])

leg = legend(dosage,'Location','northwest'); grid

[VBBV]

Alternate way is to call the scatter function inside the for loop as shown below

dpli_dris = [1,2,3,4];
hub_dris = [1,2,3,3.5];
dosage_order = [1,2,3,4];
dosage = {'1 mcg/kg/min','3 mcg/kg/min','4 mcg/kg/min','6 mcg/kg/min'};
colors = {'b','r','g','m'};
hold on
for k = 1:length(hub_dris)
    scatter(dpli_dris(k),hub_dris(k),colors{k},'filled','o','MarkerEdgeColor',[0 0 0])
end
leg = legend(dosage,'Location','northwest'); grid

[Miriam Han]

Yep. But I wanted to find a way to assign different transparency across the dosages instead of assigning a different color.

[VBBV]

Use MarkerFaceAlpha as you did earlier but with a slight change

dpli_dris = [1,2,3,4];
hub_dris = [1,2,3,3.5];
dosage_order = [1,2,3,4];
dosage = {'1 mcg/kg/min','3 mcg/kg/min','4 mcg/kg/min','6 mcg/kg/min'};
% colors = {'b','r','g','m'};
Alpha = [0.2 0.4 0.6 0.8]

Alpha = 1×4

0.2000 0.4000 0.6000 0.8000

hold on
for k = 1:length(hub_dris)
   scatter(dpli_dris(k),hub_dris(k),'b','filled','o','MarkerEdgeColor',[0 0 0],'MarkerFaceAlpha',Alpha(k))
end

leg = legend(dosage,'Location','northwest'); grid