Color each boxplot differently

I found an example that allows you to color with random colors. However, I want to color the inside of each boxplot with a certain color.

a = magic(3);
boxplot(a)
i = 3;  % number of boxplots
x = 1:i;
colors = rand(i, 3);
figure
boxplot(a, x,'Whisker', inf);

h = findobj(gca,'Tag','Box');
for j=1:length(h)
    patch(get(h(j),'XData'),get(h(j),'YData'),colors(j,:),'FaceAlpha',.5);
end

I would also like to make the lines thicker. How can I do this?

Answer 1

[Jon]

I think this should get you closer to what you want. You can select other colors using their rgb color codes, I just used red,green and blue in the example

a = magic(3);
boxplot(a)
i = 3;  % number of boxplots
x = 1:i;
colors = [1 0 0;0 1 0;0 0 1];
figure
boxplot(a, x,'BoxStyle','outline','Colors',colors);
h = findobj(gca,'Tag','Box');
for j=1:length(h)
    patch(get(h(j),'XData'),get(h(j),'YData'),get(h(j),'Color'),'FaceAlpha',.5);
end

[Jon]

You can also change the linewidth as follows

a = magic(3);
boxplot(a)
i = 3;  % number of boxplots
x = 1:i;
colors = [1 0 0;0 1 0;0 0 1];
lineWidth = 2;
figure
boxplot(a, x,'BoxStyle','outline','Colors',colors)
h = findobj(gca,'Tag','Box');
for j=1:length(h)
    set(h(j),'LineWidth',lineWidth)
    patch(get(h(j),'XData'),get(h(j),'YData'),get(h(j),'Color'),'FaceAlpha',.5);
end

[Alberto Acri]

I was interested in having an increase in the thickness of all the lines in the figure. See below:

[Jon]

If you are running R2020A or higher you may want to investigate boxchart. It seems to offer the options you want more directly

Answer 2

[Baldvin]

As has been pointed out, boxchart (documentation) was introduced in R2020a and offers flexibility with coloring of the face of boxes (and much more):

a=magic(3);
b=boxchart(a(:),'GroupByColor',repelem(1:3,3));

get(b,'BoxFaceColor')

ans = 3×1 cell array
    {[0.0660 0.4430 0.7450]}
    {[     0.8660 0.3290 0]}
    {[0.9290 0.6940 0.1250]}

This property enables you to do exactly what you want to do. For example, if you wanted to change the color of the first blue box, b(1).BoxFaceColor = 'm';

BoxChart Properties documentation, especially the "Color and Styling" section, shows many more properties that might be of interest.