How can I shade the areas when xy<0?

People much smarter than me,

I'm using the code below and want to only shade the areas in quadrants II & IV, where xy<0. Does anyone have any ideas on how to limit the shading to those regions?

Thanks for all your help, the code is below:

fig=fig+1;
figure(fig); hold on; box on; grid on
set(gcf,'Position',[0 0 5 5])
t = linspace(0, 2*pi, 200); 
x = cos(t);
y = sin(t);
H=area(x,y);
h=get(H,'children');
set(h,'FaceAlpha',0.5);

Answer 1

[Walter Roberson]

fill on angle pi/2 to pi, and 3*pi/2 to 2*pi, with the appropriate axis portions as straight lines.

By the way you might want to linspace() 201 points instead of 200

[Eric_W]

thanks for the help!