[Rd] symbols() draws squares too high (PR#9027)

[Duncan Murdoch]

On 6/23/2006 9:55 AM, michellang at gmail.com wrote:
> Full_Name: Michel Lang
> Version: 2.2.1
> OS: 2.6.16-gentoo-r9 on x86_64
> Submission from: (NULL) (62.143.164.39)
> 
> 
>   plot(-2:2, -2:2, type = "n")
>   symbols(x = 0, y = 0, squares = 2, inches = FALSE, add = TRUE)
> 
> This should plot a square with its center at (0,0) and side length 2, in other
> words a square from (-1,-1) as lower left angle to (1,1) as upper right angle.
> 
> However, if you execute this line
>   abline(h = c(-1,1))
> you see that the squares height is definitely too large.

This is not a bug.

The documentation says that when inches = FALSE, the units are those of 
the x axis, so horizontal lines are not relevant.  Try

abline(v=c(-1, 1))

If you want your x and y scales to be identical, I think you need to use 
grid and lattice, rather than traditional graphics, and to set aspect="iso".

Duncan Murdoch