[R] asp and ylim

[Greg Snow]

Look at the squishplot function in the TeachingDemos package (probably not the best named function around, but somewhat descriptive and noone has suggested a better one):

> x <- runif(100)
> y <- runif(100)
> squishplot( xlim=c(0,1), ylim=c(0.5, 0.7), asp=1 )
> plot(x,y, xlim=c(0,1), ylim=c(0.5, 0.7))

Hope this helps,

--
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 David Epstein
> Sent: Sunday, July 20, 2008 11:27 AM
> To: r-help at r-project.org
> Subject: [R] asp and ylim
>
> #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
>
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