radius = 0.0:0.5:20;
Nradius = length(radius);

for i = 1:1:Nradius
    area(i) = pi * radius(i)^2;
end
plot(radius, area, '-')
xlabel('Circle Radius, R (cm)')
ylabel('Circle Area, A (cm^2)')
title('Figure 1. The influence of radius on circle area.')