[R] precision warning in delaunayn function

[Rolf Turner]

Not answering your question but .....

     coord <- as.data.frame(coord)
     names(coord) <- c("x","y")
     require(deldir)
     tryit <- deldir(coord)
     plot(tryit)

yields the attached graph.  No problema.

     cheers,

             Rolf Turner

On 26/07/12 19:26, 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?