R help - Oct 2007 - what does "size" of a plotting character mean?

Hi,

plot(1,1, cex=2) means that the size of the plotting character (empty
circle in this case) is double the default size. Now my question is:

What characteristic of the symbol (circle) is double? Is it the area
or the diameter?

What if the symbol is not a circle, what is the generic meaning of
size in that case?

Thanks in advance,
PK

On Thu, 4 Oct 2007, Prasenjit Kapat wrote:
> Hi,
>
> plot(1,1, cex=2) means that the size of the plotting character (empty
> circle in this case) is double the default size. Now my question is:
>
> What characteristic of the symbol (circle) is double? Is it the area
> or the diameter?
Is it not obvious when you try it?  Diameter.
> What if the symbol is not a circle, what is the generic meaning of
> size in that case?
cex does linear scaling in each dimension.

There is no generic definition of what cex=1 means: it depends on the 
device, the font (for pch >=32 except ".") or the symbols
(pch=1...25).

-- 
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

Hi,

Thank you Prof Ripley for the response.

On 10/4/07, Prof Brian Ripley <ripley at stats.ox.ac.uk>
wrote:
> On Thu, 4 Oct 2007, Prasenjit Kapat wrote:
>
> > Hi,
> >
> > plot(1,1, cex=2) means that the size of the plotting character (empty
> > circle in this case) is double the default size. Now my question is:
> >
> > What characteristic of the symbol (circle) is double? Is it the area
> > or the diameter?
>
> Is it not obvious when you try it?  Diameter.
>
> > What if the symbol is not a circle, what is the generic meaning of
> > size in that case?
>
> cex does linear scaling in each dimension.
I was hoping this would be true.
>
> There is no generic definition of what cex=1 means: it depends on the
> device, the font (for pch >=32 except ".") or the symbols
(pch=1...25).

Thanks
PK