function y = drums(R,n)
% DRUMS:  y = drums(R,n)
%  Uses numgrid to show eigenmodes of various drums.
%  Options for R are same as in numgrid;
%       'S','L','C','A','D','H','B','N'
%  Note 'S' and 'N' produce the same picture but 'N' should run faster.
%  See sqgridorder for explanation of 'N'.  Also note use of subplot.
%  Try "drums('L',20)".
%  (Tim Carlson, 2/02)
%  Mods,comments ELB.

if mod(n,2) == 0, n = n+1; end

g = numgrid(R,n);
x=-1:2/(n-1):1;  %only for axis purposes
u = delsq(g)*n*n;
[w,d] = eigs(u,3,0);

for l=1:3      
   h = zeros(n);
   v=w(g(g>0),l);
   h(g>0)=v/norm(v,inf);
   subplot(2,2,l), mesh(x,x,h);
   axis tight, title(['evalue = ' num2str(d(l,l))]);
end

subplot(2,2,4), contour(x,x,g>0), axis([-1 1 -1 1])