I've accomplished this feature via: ax = axis() set(gca().

    > hlines([0.], ax[0], ax[1])[0], linewidth=1)

    > I don't remember why I did it this way instead of just
    > plotting. Maybe I thought is was more clever. Does this
    > method avoid auto-scaling? -g

Yes it does, only because hlines doesn't call autoscale (I just looked
it up). This is probably a bug, since I don't see why the plot and
hlines method should have different behavior. It looks like an

I think plotting the horizontal extent in axes coords is the proper
way to go.