R help - Oct 2008 - draw a 5cm x 3cm rectangle

Hi I want to draw sth in a pdf file with a predefined defined size.
Say a 5cm x 3cm rectangle (a ruler):

pdf("rect.pdf", paper="a4")
plot(c(1,5,5,1,1),c(1,1,3,3,1),asp=1,axes="n")
dev.off()

but how do I fix that one unit is 1cm?
Thanks
thomas

2008/10/16 Thomas Steiner <finbref.2006 at
gmail.com>:
> Hi I want to draw sth in a pdf file with a predefined defined size.
> Say a 5cm x 3cm rectangle (a ruler):
>
> pdf("rect.pdf", paper="a4")
> plot(c(1,5,5,1,1),c(1,1,3,3,1),asp=1,axes="n")
> dev.off()
>
> but how do I fix that one unit is 1cm?
 I just did help.search("inch") and found xinch:

     'xinch' and 'yinch' convert the specified number of inches
given
     as their arguments into the correct units for plotting with
     graphics functions.  Usually, this only makes sense when normal
     coordinates are used, i.e., _no_ 'log' scale (see the 'log'
     argument to 'par').

 Then help.search("cm") gave me cm:

Description:

     Translates from inches to cm (centimeters).

 You just need the inverse of this. Not too hard.

 Also, the symbol() function takes an inches=TRUE parameter that lets
you specify inches as the object size.

 The grid graphics package has a units system as well, but I've not
played with that. See help("unit") for info.

Barry