[R] precision warning in delaunayn function
Jean-Luc Dupouey
dupouey at nancy.inra.fr
Thu Jul 26 09:26:12 CEST 2012
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
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