Martha - according to poly2mask, there are only four inputs to this function. You have specified five, so the error message Error using poly2mask Too many input arguments makes sense.
Your code is almost correct, it is just the assignment (and additional fifth parameter) that needs some work. Perhaps the following with do the trick
polygons=zeros(612,924,count);
for w=1:1:count;
polygons(:,:,w)=poly2mask(x(:,w),y(:,w),sf(1),sf(2));
end
Try the above and see what happens!
