How to use the patch function for a cone

I am trying to complete a homework assignment, but I am having trouble on the last task. I am supposed to use the patch function to create a figure of a cone. The cone has a radius of 20, has a height of 30, and comes to its peak at (0,0). Here is what i have tried:

th=0:.1:(2*pi);

r=20;

z=-30;

for i=1:length(th)

     x(i)=r*cos(th(i));

     y(i)=r*sin(th(i));

end

cone.vertices=[x, y, z;
               0, 0, 0];

cone.faces=[1, 2];

figure(4)

ph=patch(cone);

ph.EdgeColor=[0, 0, 0];

ph.FaceColor=[.1, .5, .9];

ph.LineWidth=2;

Any help would be appreciated, Thanks!

Answer 1

[KSSV]

M = 20 ; N = 50 ;  % can be varied 
R0 = 2 ;  % Radius of cone 
H = 2 ;   % height of cone 
m = H/R0 ;
nT = linspace(0,2*pi,M) ;   % angles 
nR = linspace(0,R0,M) ;     %  Radius 
[T, R] = meshgrid(nT,nR) ;
% Convert grid to cartesian coordintes
XX = R.*cos(T) ; 
YY = R.*sin(T) ;
ZZ = m*R ;
surf(XX,YY,ZZ) ;

[ckc]

That does give the correct graph that i am looking for, except i need it to be one solid color and not have the grids. Thank you!

[KSSV]

Try:

surf(XX,YY,ZZ,0*ZZ,'edgecolor','k')