# Re: [R] Convex hull line coordinates..

From: Clint Bowman <clint_at_ecy.wa.gov>
Date: Tue 22 Mar 2005 - 04:24:42 EST

?chull

states:

Value:

```     An integer vector giving the indices of the points lying on the
convex hull, in clockwise order.

```

therefore (see Example in ?chull) you have the end points of each line segment from which you can compute the equation of each line segment. Since the precision of the calculation is finite, there will necessarily be some portion of each line that may fall on one side or the other of the "true" convex hull.

Or am I off base?

Clint

On Mon, 21 Mar 2005, Romain Francois wrote:

> Hello,
>
> I'm not sure i got your question right, but i think the whole point is
> to find the equation of a line which passes by two points
> See ?lm
>
> Romain.
>
>
> Le 21.03.2005 11:09, achilleas.psomas@wsl.ch a écrit :
>
> >Hello R-Helpers..
> >
> >I am still new in R and I have the following question..
> >I am applying the function chull on a 2D dataset and have the convex hull
> >nicely
> >calculated and plotted.
> >Do you know if there is a way to extract the coordinates of the line created
> >from the connection of the chull data points..
> >I have alredy tried with "approx" to lineary interpolate but its not working
> >correctly since the interpolated values sometimes fall inside the convex .
> >Using the "yleft" or "yright" doesnt seem to help..
> >
> >Any suggestions?

> >
> >Achilleas Psomas
> >
> >______________________________________________
> >R-help@stat.math.ethz.ch mailing list
> >https://stat.ethz.ch/mailman/listinfo/r-help
> >
> >
> >
> >
>
>
>

```--
Clint Bowman			INTERNET:	clint@ecy.wa.gov
Air Quality Modeler		INTERNET:	clint@math.utah.edu
Department of Ecology		VOICE:		(360) 407-6815
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