R help - Aug 2009 - setting par(srt) according to plot aspect ratio

How can I look up the aspect ratio of a plot, so I can use that to correctly
adjust the angle of text which is supposed to be parallel to a line in the
plot?

The following example code works for a 1:1 aspect ratio, but puts the text
at the wrong angle if the plot region is short and wide or tall and narrow.
 I can't find a par() component containing the plot aspect ratio.  It will
be for png() or postscript() output, if that matters.

f <- function(x) x
g <- function(x) 2*x
(f_angle <- atan(1)*180/pi)
(g_angle <- atan(2)*180/pi)
xpos <- 0.2
plot(f)
plot(g,add=TRUE)
par(srt=f_angle)
text(xpos,f(xpos),label="y=x",pos=3)
par(srt=g_angle)
text(xpos,g(xpos),label="y=2x",pos=3)


-- 
Levi Waldron
post-doctoral fellow
Jurisica Lab, Ontario Cancer Institute
Division of Signaling Biology
TMDT 9-304D
101 College Street
Toronto, Ontario M5G 1L7
(416)581-7453

	[[alternative HTML version deleted]]

I frequently use R's help facilities and I know about the asp argument to
plot, but this doesn't answer my question.  I would like to allow the aspect
to be determined automatically but *query* the aspect ratio for future use.

I suppose one work-around would be to use the data ranges and plot region
dimensions to estimate an appropriate value for asp, but this more
complicated than I was hoping for.

Thanks,
Levi

On Thu, Aug 27, 2009 at 6:19 PM, Bert Gunter <gunter.berton@gene.com>
wrote:
> Use R's help facilities, please.
>
> help.search("aspect ratio")
>
> gets you to ?plot.window
>
> which then gets you to ?plot (actually plot.default() )
>
> Bert Gunter
> Genentech Nonclinical Biostatisics
>
> -----Original Message-----
> From: r-help-bounces@r-project.org [mailto:r-help-bounces@r-project.org]
> On
> Behalf Of Levi Waldron
> Sent: Thursday, August 27, 2009 1:54 PM
> To: r-help@r-project.org
> Subject: [R] setting par(srt) according to plot aspect ratio
>
> How can I look up the aspect ratio of a plot, so I can use that to
> correctly
> adjust the angle of text which is supposed to be parallel to a line in the
> plot?
>
> The following example code works for a 1:1 aspect ratio, but puts the text
> at the wrong angle if the plot region is short and wide or tall and narrow.
>  I can't find a par() component containing the plot aspect ratio.  It
will
> be for png() or postscript() output, if that matters.
>
> f <- function(x) x
> g <- function(x) 2*x
> (f_angle <- atan(1)*180/pi)
> (g_angle <- atan(2)*180/pi)
> xpos <- 0.2
> plot(f)
> plot(g,add=TRUE)
> par(srt=f_angle)
> text(xpos,f(xpos),label="y=x",pos=3)
> par(srt=g_angle)
> text(xpos,g(xpos),label="y=2x",pos=3)
>
>
> --
> Levi Waldron
> post-doctoral fellow
> Jurisica Lab, Ontario Cancer Institute
> Division of Signaling Biology
> TMDT 9-304D
> 101 College Street
> Toronto, Ontario M5G 1L7
> (416)581-7453
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@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.
>
>

-- 
Levi Waldron
post-doctoral fellow
Jurisica Lab, Ontario Cancer Institute
Division of Signaling Biology
TMDT 9-304D
101 College Street
Toronto, Ontario M5G 1L7
(416)581-7453

	[[alternative HTML version deleted]]

On Fri, Aug 28, 2009 at 1:48 AM, Prof Brian Ripley
<ripley@stats.ox.ac.uk>wrote:
> Note that the aspect ratio changes when you resize the plot but the angle
> of the plotted text will not.  So the only safe route is to set
'asp' and
> use that setting to select the angle.

That is true with screen output, although I can run the code block again
after re-sizing to correct the text angle along with the aspect ratio.  And
for my purpose which is writing to file, it isn't an issue, for example the
following plots which need different aspect ratios all work correctly:

png("example%d.png")
makeplot()  #as per example code
par(mfrow=c(2,1))
makeplot()
makeplot()
par(mfrow=c(1,2))
makeplot()
makeplot()
dev.off()


-- 
Levi Waldron
post-doctoral fellow
Jurisica Lab, Ontario Cancer Institute
Division of Signaling Biology
TMDT 9-304D
101 College Street
Toronto, Ontario M5G 1L7
(416)581-7453

	[[alternative HTML version deleted]]