R help - Sep 2008 - how to draw a vertical line from points to x-axis

Hello,

I want to know how to draw a line connecting each point to the x-axis
perpendicularly (i.e. a vertical line).
abline(v=...) seems not to work for my purpose, because it runs over the
data point. Can anyone help? Thanks.

Anny

	[[alternative HTML version deleted]]

Anny

Here's one way:

plot(0:10, 0:10, pch=16)
lines(rep(0:10, each=3), t(matrix(c(0:10, rep(c(0,NA), each=11)),
ncol=3))) 

HTH ....

Peter Alspach

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Anny Huang
> Sent: Monday, 8 September 2008 8:49 a.m.
> To: r-help at r-project.org
> Subject: [R] how to draw a vertical line from points to x-axis
> 
> Hello,
> 
> I want to know how to draw a line connecting each point to 
> the x-axis perpendicularly (i.e. a vertical line).
> abline(v=...) seems not to work for my purpose, because it 
> runs over the data point. Can anyone help? Thanks.
> 
> Anny
> 
> 	[[alternative HTML version deleted]]
> 
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2008/9/7 Anny Huang <annylhuang at gmail.com>:
> Hello,
>
> I want to know how to draw a line connecting each point to the x-axis
> perpendicularly (i.e. a vertical line).
> abline(v=...) seems not to work for my purpose, because it runs over the
> data point. Can anyone help? Thanks.
>
 If your x-axis is at y=zero then plot with type='h' will do this:

   plot(1:10,runif(10),type='h',ylim=c(0,1))

 but it will draw lines *up* if the value is negative:

   plot(1:10,(1:10)-5,type='h')

 Or do you really want the lines to come right down to the axis line?
In which case a modified version of Peter Alspach's solution which
goes down to the limit of the plot instead of zero should work. See
help(par) for what par()$usr is all about.

 y= 6+0:10
 x=0:10
 plot(x,y,pch=16,ylim=c(-2,17))
 lines(rep(x,each=3),t(matrix(c(y,rep(c(par()$usr[3],NA),each=11)),ncol=3)))

Barry

I think you want the ?lines function.

To connect a point (x,y) to the x-axis,

lines(x=c(x,x),y=c(y,0))

...draws a line from that point to the x-axis. You may also want to specify
pch=c(?,""),type="b" where ? is the original point type
(which you don't
want to "run over") and "" is the pch for theline on the
axis.

--Adam

On Sun, 7 Sep 2008, Anny Huang wrote:
> Hello,
>
> I want to know how to draw a line connecting each point to the x-axis
> perpendicularly (i.e. a vertical line).
> abline(v=...) seems not to work for my purpose, because it runs over the
> data point. Can anyone help? Thanks.
>
> Anny
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>