[R] drawing segments through points with pch=1

[Paul Smith]

On Sun, Jul 20, 2008 at 1:44 PM, David Epstein
<David.Epstein at warwick.ac.uk> wrote:
> Please excuse me for asking such basic questions:
>
> Here is my code
>>
>> y=c(1.21,0.51,0.14,1.62,-0.8,0.72,-1.71,0.84,0.02,-0.12)
>> ybar=mean(y)
>> ll=length(y);
>> ybarv=rep(ybar,ll)
>> x=1:ll
>> plot(x,ybarv,pch=1)
>> segments(x[1],ybar,x[ll],ybar)
>
> What I get is a collection of small circles, with a segment "on top" of the
> circles, which is almost what I want. But I don't want the segment to be
> visible inside any small circle.
>
> Is there an easy way to arrange for the segment to "lie behind" the pch=1
> markers, as in hidden line removal, so that the circles remain with nothing
> inside them? I tried putting the segments command first, but then no segment
> appeared at all.
>
> In general, is there a method of laying a drawing "on top" of another. I
> tried inserting add="T" as an argument to plot, and R objected strongly.

What about replacing

segments(x[1],ybar,x[ll],ybar)
plot(x,ybarv,pch=1)

with

plot(x,ybarv,type="b")

?

Paul