[R] How to add grid lines at specific position to a plot?

[Sarah Goslee]

abline(h=0)

On Thu, Mar 15, 2012 at 1:05 PM, Michael <comtech.usa at gmail.com> wrote:
> How to add grid lines at specific position to a plot?
>
> Hi all,
>
> [Disclaimer: I have done extensive and intensive searching on Google and
> asked around but couldn't find a solution to this problem.
> Please help me instead of just pointing out how simple and stupid my
> question is. God bless good folks! Thanks!]
>
> This is a headache for me and I have been struggling with this for a while.
>
> With an existing plot, how can I add a horizontal grid line at vertical
> location 0 (just need 1 grid line)...
>
> I can certainly draw such a line myself using "lines".
>
> However, that will impact my legends because that also counts as a line.
> But we wouldn't want a grid line to be counted as a line...
>
> Could anybody please help me?
>
> Thanks!
>

-- 
Sarah Goslee
http://www.functionaldiversity.org