The easiest way to do that would be to use the axis function, possibly including the handle graphics function to set the YTick positions and labels. Experiment with something like:
x = linspace(0,2*pi,250);
y = sin(4*x).^2;
figure(1)
plot(x, y)
axis([0 2*pi -0.05 1]);
set(gca, 'YTick', [0 1])
until you get the result you want.
