Hi shane, filling with a pattern isn't trivial so I recommend the functions listed in the file exchange. However, here's a fairly easy way to add a polka dot pattern to the area being filled.
The coordinates used to fill form a polygon. This makes an array of random dots that span the size of your polygon and then it removes any dots that are outside of the polygon.
See inline comments for details.
% Here are the coordinates of your polygon used in fill()
polyX = [x,fliplr(x)];
polyY = [y,bottom*ones(size(y))];
viu=fill(polyX,polyY,[0 1 0])
viu.FaceAlpha = 0.2;
% Create array of polkadot coordinates that span the size of the polygon
[dotsX,dotsY] = ndgrid(...
min(polyX): 1 : max(polyX), ...
min(polyY): 1 : max(polyY));
% Determine which coordinates are on or in your polygon
[in,on] = inpolygon(dotsX,dotsY,polyX,polyY);
% extract coordinates in or on polygon
inX = dotsX(in|on);
inY = dotsY(in|on);
% Plot polkadots
hold on
h = plot(inX,inY,'k.','MarkerSize',4,'MarkerFaceColor','k');
