[R] precision warning in delaunayn function

[Keith Jewell]

Does

 > delaunayn(scale(coord),options="Qbb")

help?

Keith J

On 26/07/2012 08:26, Jean-Luc Dupouey wrote:
> Dear R helpers,
>
> I try to use the 'delaunayn' function in the 'geometry' package for
> Delaunay triangulation in 2 dimensions.
>
> For the four following points, I get a warning message :
>
>  > coord=matrix(ncol=2,byrow=TRUE,c(622633,7073452,
> + 621228,7073517,
> + 621879,7071762,
> + 621065,7073331))
>  > library(geometry)
>  >
>  > test=delaunayn(coord,options="Qbb")
>
> qhull precision warning:
>
> The initial hull is narrow (cosine of min. angle is 0.9999999999999999).
> Is the input lower dimensional (e.g., on a plane in 3-d)? Qhull may
> produce a wide facet. Options 'QbB' (scale to unit box) or 'Qbb' (scale
> last coordinate) may remove this warning. Use 'Pp' to skip this warning.
> See 'Limitations' in qh-impre.htm.
>
> I read carefully qh-impre.htm and I still do not understand why I get
> this message. A simple call to plot(coord) shows that the points are not
> aligned, nor very close.
>
> What did I miss?
>
> Thanking you in advance,
>
> Jean-Luc Dupouey
> INRA-Lorrain University
> Forest Ecology & Ecophysiology Unit
> F-54280 Champenoux
> France
> mail: dupouey at nancy.inra.fr
>