function roots = datazero(w)
% assumes domain w(1,:) range w(2,:)
x = w(1,:); y = w(2,:); ay = abs(y);
jy = ay(1:end-1)+ay(2:end);
oscilate = y(1:end-1) .* y(2:end);
i = find(oscilate < 0);
g0 = (ay(i+1).*x(i)+ay(i).*x(i+1))./jy(i);
d0 = x(find(y==0));
roots = sort[d0 g0];
