Controlling the extent of ablines on plot

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Hi all,

I'm attempting to make a quite-specific plot where the axes cross at the
origin and with gridlines for guidance. I've been using ablines to create
the reference lines because I want a lot of control as to where they are
placed on the axis. This command works very well for such control.
However...

These ablines don't seem to work when I specify the origin as 0,0. They go
beyond the x-axis at both ends, rendering a quite ugly graph (and they push
back the y-axis title some).

Behold:

###
x<-c(0,1,2,3,4,5)
y<-c(0,2,4,6,8,10)

plot(x,y, axes=FALSE)
axis(1,at=c(0,1,2,2.5,3,4,5),pos=0)
axis(2,at=c(0,2,4,6,8,10),pos=0)
abline(h=c(1,2,3,4,5))
###

Is there any way for me to specify that these ablines should not go beyond
the y-axis extent? I just want a pretty graph!

Thanks!
Ryan

Maybe you could use lines()?

plot(1:2)
lines(c(1,2),c(1.5,1.5))
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Check your par() settings, specifically "xpd".  For more control see ?clip.  If that does not do enough for you then use lines or segments for complete control.
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org
801.408.8111

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Ryan Utz
> Sent: Tuesday, May 03, 2011 10:36 AM
> To: r-help at r-project.org
> Subject: [R] Controlling the extent of ablines on plot
> 
> Hi all,
> 
> I'm attempting to make a quite-specific plot where the axes cross at
> the
> origin and with gridlines for guidance. I've been using ablines to
> create
> the reference lines because I want a lot of control as to where they
> are
> placed on the axis. This command works very well for such control.
> However...
> 
> These ablines don't seem to work when I specify the origin as 0,0. They
> go
> beyond the x-axis at both ends, rendering a quite ugly graph (and they
> push
> back the y-axis title some).
> 
> Behold:
> 
> ###
> x<-c(0,1,2,3,4,5)
> y<-c(0,2,4,6,8,10)
> 
> plot(x,y, axes=FALSE)
> axis(1,at=c(0,1,2,2.5,3,4,5),pos=0)
> axis(2,at=c(0,2,4,6,8,10),pos=0)
> abline(h=c(1,2,3,4,5))
> ###
> 
> Is there any way for me to specify that these ablines should not go
> beyond
> the y-axis extent? I just want a pretty graph!
> 
> Thanks!
> Ryan
> 
> --
> 
> Ryan Utz, Ph.D.
> Aquatic Ecologist/STREON Scientist
> National Ecological Observatory Network
> 
> Home/Cell: (724) 272-7769
> Work: (720) 746-4844 ext. 2488
> 
> 	[[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.
Hi Ryan,

The issue is the plotting region is slightly padded.  The easiest
option, I think, would be to clip() it.  I have a general sense that
one of the par() options would let you adjust the padding to 0, but I
could just be imagining that (anyone else??).  Anyway, here are some
options:

###
plot(0:5, seq(0, 10, 2), axes=FALSE)
axis(1, at=c(0,1,2,2.5,3,4,5), pos=0)
axis(2, at=seq(0, 10, 2), pos=0)
## using clip and abline
clip(0, 5, 0, 10)
abline(h = 1:5)
dev.new()
plot(0:5, seq(0, 10, 2), axes=FALSE)
axis(1, at=c(0,1,2,2.5,3,4,5), pos=0)
axis(2, at=seq(0, 10, 2), pos=0)
## using lines, but without retyping as much
sapply(1:5, function(y) lines(c(0, 5), c(y, y)))
## or even easier, getting the same thing with segments
segments(0, 1:5, 5, 1:5)

HTH,

Josh
Well... that could work. Problem is in the actual graphs I'm making, there
are to be >30 lines per graph (as many as 60 in some cases). Any way I could
use the lines command without having to write out 60 lines of code per
figure? That's why I like ablines; you just have to specify a single value
and it will put a horizontal line at that number.

Thanks,
Ryan

Maybe you could use lines()?

plot(1:2)
lines(c(1,2),c(1.5,1.5))

--

Ryan Utz, Ph.D.
Aquatic Ecologist/STREON Scientist
National Ecological Observatory Network

Home/Cell: (724) 272-7769
Work: (720) 746-4844 ext. 2488

? ? ? ?[[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.

Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/
The issue is the plotting region is slightly padded. ?The easiest
option, I think, would be to clip() it. ?I have a general sense that
one of the par() options would let you adjust the padding to 0, but I
could just be imagining that (anyone else??).
Not loving it, but this is sort of what I meant...

plot(0:5, seq(0, 10, 2), axes=FALSE, xaxs = "i", yaxs = "i")
axis(1, at=c(0,1,2,2.5,3,4,5), pos=0)
axis(2, at=seq(0, 10, 2), pos=0)
abline(h = 1:5)
Well... that could work. Problem is in the actual graphs I'm making, there
are to be>30 lines per graph (as many as 60 in some cases). Any way I could
use the lines command without having to write out 60 lines of code per
figure? That's why I like ablines; you just have to specify a single value
and it will put a horizontal line at that number.

Thanks,
Ryan
Write your own abline.  For example, with your previously posted example:

xlim <- c(0, 5)
ylim <- c(0, 10)

abline2 <- function(h, v) {
   if (!missing(h)) {
     n <- length(h)
     segments( rep(xlim[1], n), h, rep(xlim[2], n), h)
   }
   if (!missing(v)) {
     n <- length(v)
     segments( rep(ylim[1], n), v, rep(ylim[2], n), v)
   }
}

Just replace your abline() call with abline2().

Duncan Murdoch