[R-sig-Geo] create a asymmetric ellipse

[Barry Rowlingson]

On Tue, Mar 23, 2010 at 4:27 AM, gianni lavaredo
<gianni.lavaredo at gmail.com> wrote:
> Dear Researchers,
>
> nobody know same fuction to draw an asymmetric ellipse as the fig starting
> from a data.frame
>
> cc <- data.frame(ID = 1, xx= 4256300, yy= 336235, N = 5.3, S= 2.1, W = 3.5,
> E= 0.3)
>
> or
>
> cc <- data.frame(ID = 1, xx= 4256300, yy= 336235, y = 7.4, x=3.8)
>
> where xx and yy are the coordiante of centre
> thanks for help (i need)

 This looks like a very strange shape - I'm not sure just saying
'asymmetric ellipse' is good enough.

 Are you after any smooth curve centred at (x,y) passing through
(x+W,y), (x,y+N), (x-E,y), (x,y-S)?

 Do you require the gradients of the curve to be 0 or infinite (ie the
tangent is horizontal or vertical) at those four points?

 How smooth (differentiable) do you want it to be? Could it just be
defined in polar coordinates as four elliptical parts?

 Do you want some kind of 'Oval'? Any of the ones mentioned here take
your fancy:

http://mathworld.wolfram.com/Oval.html

Barry