Re: [R] drawing segments through points with pch=1

From: Prof Brian Ripley <ripley_at_stats.ox.ac.uk>
Date: Sun, 20 Jul 2008 14:54:04 +0100 (BST)

> making the plot without points (plot(....., type="n")), drawing segments and
> at the end paint points with white background colour in order to "overwrite"
> the segments:

Except that the background is not necessarily white (and you may want it to be transparent or translucent).

It looks to me like lines(type="b") might be what was wanted.

> 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, type="n")
> segments(x[1], ybar, x[ll], ybar)
> points(x, ybarv, pch=21, bg="white")
>
>
>
> Uwe Ligges
>
>
>
> David Epstein wrote:
>>
>> 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.
>>
>> Thanks for any help
>>
>> David Epstein
>>
>> ______________________________________________
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>> and provide commented, minimal, self-contained, reproducible code.
>
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> and provide commented, minimal, self-contained, reproducible code.
>

```--
Brian D. Ripley,                  ripley_at_stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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