How to fill the area between two function on a plot with transparent colour?

Is it possible to fill the area between two function on a plot with transparent colour?

Answer 1

[Mischa Kim]

It is. Try, e.g.

 d = 0.1;
 x = linspace(0,1,20);
 z = d*x.^2;

 fill([x flip(x)],[z zeros(size(z))],'k','LineStyle','none')
 hold on
 plot(x,z,'k-');
 alpha(0.25)
 grid

[Ruoyao]

Thank you Mischa, your answer was very helpful! Then I added the legend, but the colors in the legend were still solid. How could I make them transparent as well? Thanks!

[Ruoyao]

I found answer on this webpage: https://stackoverflow.com/questions/23693210/setting-the-alpha-value-transparency-of-legend-to-match-alpha-in-plot-in-matla