For your box plot, experiment with this to get the result you want:
d = randi(10, 20, 3);
figure(1)
boxplot(d)
yt = get(gca, 'YTick');
axis([xlim 0 ceil(max(yt)*1.2)])
xt = get(gca, 'XTick');
hold on
plot(xt([2 3]), [1 1]*max(yt)*1.1, '-k', mean(xt([2 3])), max(yt)*1.15, '*k')
hold off
The ‘xt’ and ‘yt’ variables get the x-tick and y-tick values, and are then used to do the ‘sigline’ and asterisk calculations on. The axis call simply creates room at the top of the plot box for the line and asterisk.
