[R] surfaces and digital terrain model

[Thomas W Blackwell]

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
>