Aspect ratio and limits

# Set height value as you require
height <- 3
X11(width = aspect * height, height = height)
.... 
Does that get you what you need?

I'm guessing that will work, but it just seems unsatisfactory, since 
if I resize my graphics window I mess it up.

  If I set par(pty='s') I can have a square plot floating inside a 
graphics window of any shape, I'd like to be able to plot something 
specifying ylim and asp and get a rectangular plot with a fixed aspect 
ratio floating around inside a resizable graphics device....

  The 'aspect' ratio of xyplot (lattice package) lets you specify the 
aspect ratio of the plot (not relating to the data, ie aspect=1 draws a 
square plot whatever the ratio of X and Y range). Try this:

  xy=data.frame(x=c(0,21),y=c(0,4))
  xyplot(y~x,data=xy,aspect=0.2)

  - now resize the graphics window and the plot keeps its ratio. That's 
the effect I was hoping to get from base graphics.

  I could use lattice graphics but I'd have to work out the value of 
'aspect' to get the 1:1 aspect ratio for my data. I'm not sure this is 
trivial, since it may involve considering the various margins and 
spacing around a plot.

  Close...

Baz