The easiest way I know is to use the fill function documented here. Take all the x and y data from your arcs using
%you may have to do this between each circle_th use if you don't have
%another way of getting the x and y data
ax = gca; %get the axis with all your curves
x = ax.Children.XData; %grab x data
y = ax.Children.YData; %grab y data
You may need to adjust your curves and line them up head to tail using the flip function like this.
x1 = (1:20)';
y1 = x1.^2;
plot(x1,y1)
x2 = (10:0.5:20)';
y2 = 0.5*x2.^2+200;
hold on
plot(x2,y2)
x3 = [x1(1);x2(1)];
y3 = [y1(1);y2(1)];
plot(x3,y3)
x = [x1;flip(x2);x3];
y = [y1;flip(y2);y3];
fill(x,y,'r')
hold off
