Message-ID: <Pine.SOL.4.44.0305300814500.4891-100000@timepilot.gpcc.itd.umich.edu>
Date: 2003-05-30T12:35:16Z
From: Thomas W Blackwell
Subject: surfaces and digital terrain model
In-Reply-To: <3ED65B8E.7050703@sentoo.sn>
Renaud -
help("contour") gives a reference to filled.contour(), which might
do what you want by explicitly setting its "levels" argument to be
the single z value which corresponds to the water level. I have not
experimented to see whether filled.contour() will accept arguments
new=FALSE, add=TRUE which would allow it to add to an existing plot.
And, my information is relative to base R 1.6.1. More recent versions
of R may have other function names, such as "levelplot". Try the
help().
- tom blackwell - u michigan medical school - ann arbor -
On Thu, 29 May 2003, Renaud Lancelot wrote:
> Dear all,
>
> I have computed a digital terrain model from a set of points (x, y, z)
> using the function interp() in package akima. I want to predict flooded
> surfaces given target values of z. I can display the flooded surfaces
> with contour() or image(), but I don't know how to get the polygons
> delimiting the surfaces. Did anyone write a function for this purpose ?
>
> Dr Renaud Lancelot, vétérinaire
> CIRAD, Département Elevage et Médecine Vétérinaire (CIRAD-Emvt)
> Programme Productions Animales
> http://www.cirad.fr/presentation/programmes/prod-ani.shtml
>
> ISRA-LNERV tel (221) 832 49 02
> BP 2057 Dakar-Hann fax (221) 821 18 79 (CIRAD)
> Senegal e-mail renaud.lancelot at cirad.fr
>