[R] 'symbols' not plotting correct circle radii

[Jim Lemon]

On 07/18/2012 08:02 PM, Stuart Leask wrote:
> Hi there.
>
> I have been plotting some circles using 'symbols', with radii representing my data, but the radii looked incorrect.
>
> It seems to happen with a single circle too:
>
> Symbols ( 0, 0, circles = 40, xlim = c(-40, 40), ylim= c(-40, 40))
>
> If I put a ruler up to my monitor (technology!)  to compare the radius with the axes, the circle isn't radius 40; it is closer to 15...
>
> I suspect there is a simple answer.
>
Hi Stuart,
The answer does not appear to be simple. While the documentation for 
symbols says that the "inches" argument controls the size of the 
circles, it appears to do so with reference to the user units of the 
plot, not to that quaint unit descending from the twelfth part of 
someone's foot. So, whatever numbers you pass as "circles" seem to be 
scaled to a maximum dimension of whatever "inches" is in user units, at 
least on the x11 graphics device.

Jim