Erase area of matlab plot a posteriori

Question

Is it possible to erase an area of a plot, without direct manipulation of the data that you input to the plot (a posteriori)?

E.g. Area below y=x while the area above is kept.

Answer 1

You can use area with white face color to blank the area of the plot below a given line:

t = linspace(0,20,500);
plot(t, sin(t)) % example plot
yl = ylim;
hold on
y = .4 - t * .05; % example limit line
area(t, y, yl(1), 'Facecolor', 'w', 'edgecolor', 'none');