clear;

r1=0; dr=0.05; r2=1;
a1=0; da=2*pi/50; a2=2*pi;

rint=r1:dr:r2;
aint=a1:da:a2;

X=rint'*cos(aint); 
Y=rint'*sin(aint); 

R = rint'*ones(size(aint));
TH = ones(size(rint'))*aint;

n=4;
surf(X,Y,R.^n.*cos(n.*TH)); shading faceted;
colormap jet;
