# Re: [R] asp and ylim

From: David Epstein <David.Epstein_at_warwick.ac.uk>
Date: Mon, 21 Jul 2008 09:42:35 +0100

Perhaps the best solution is to live with plot() as it is. If I need the picture for a paper, I will export data to Matlab or Mathematica or Illustrator, where I can get the control I want.

David

On 20 Jul, 2008, at 23:14, Prof Brian Ripley wrote:

> Take a look at eqscplot() in package MASS for a different approach.
>
> You last para forgets that once you have set the device region and
> the margins the physical plot region and hence its aspect ratio is
> determined -- see the figures in 'An Introduction to R'.
>
> On Sun, 20 Jul 2008, David Epstein wrote:
>
>> #See David Williams' book "Weighing the odds", p286
>>
>> 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)
>> ylength <- length(y)
>> ybarv <- rep(ybar, ylength)
>> x <- 1:ylength
>> plot(x,y,asp=1,xlab="position",ylab="ybar",type="n",ylim=c(-1,1))
>> segments(x[1], ybar, x[ylength], ybar)
>> segments(x,ybarv,x,y)
>> points(x, ybarv, pch=21, bg="white")
>> points(x,y,pch=19,col="black")
>>
>> With asp=1, the value of ylim seems to be totally ignored, as in
>> the above code. With asp not set, R plays close attention to the
>> value of ylim. This is not intuitive behaviour, or is it?
>>
>> How can I set the aspect ratio, and simultaneously set the plot
>> region? The aspect ratio is one number and the plot region is
>> given by four numbers (xleft, xright, yleft, yright). Logically,
>> these 5 numbers are independent of each other and arbitrary,
>> provided xleft<xright and yleft<yright. This should give a one-to-
>> one bijection between 5-tuples and plots, determined up to a
>> change of scale that is uniform in the x- and y-dirctions. My code
>> above shows the (to me) obvious attempt, which fails.
>>
>> Thanks
>> David
>>
>> ______________________________________________
>> R-help_at_r-project.org mailing list
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>> guide.html
>> 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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