Plot Stiffness of Unidirectional Composite in Polar Coordinate System

I would like to recreate the following diagramm in Matlab. Throught the funktion polarplot(theta,rho) I was already able to create the figure, but I lack the knowlege to fill in the correct inputs für theta and rho. Thanks for the help.

Answer 1

[J. Alex Lee]

theta and rho are respectively angle and radius...so for example

t = linspace(0,2*pi,500)';
r = cos(t).^4 + .5;
polarplot(t,r);
hold on
r = cos(t+pi/2).^4 + .5;
polarplot(t,r);
r = 0.5*cos(t-pi/4).^4 + 0.5*cos(t+pi/4).^4 + .0;
polarplot(t,r);

[Julien Trekel]

Thank you so much!