R help - Mar 2006 - Controlling (number of) wires in wireframe

Hi,

I would like to plot a wireframe (library: lattice) of the function f 
(x,y)=x*y where x and y are equally evaluated between 0 and 1.
When one uses the option drape=TRUE then each "square" between the  
"wires" (lines that build the surface shape) gets a certain color. A  
perfect wireframe plot of a continuous surface would be, if you  
(almost) can not distinguish between the colors of those "squares"  
that lie adjacent to each other. So the idea would be, to choose many  
many evaluation points for x (and y), say x (and y) consists of 1000  
equally spaced intermediate points. But the problem is, that there  
are too many "wires" plotted... the whole picture is dark... On the  
other hand, if you use only 20 points for the x (and also y) axis,  
then you get a really nice wired frame, but the colors for each  
"square" differ a lot (if you do not think that they differ a lot  
then just think of plotting a different function and this "color- 
problem" appears again). So the solution would be, to choose many  
many values for x (and y) _but_ only to plot wires -say- every 10th  
time, the color changes, i.e. not to plot _all_ wires but only a  
subset (every 10th wire for example). Is that possible?? How??

Thanks in advance

marius

On 3/4/06, Jan Marius Hofert <m_hofert at web.de>
wrote:
> Hi,
>
> I would like to plot a wireframe (library: lattice) of the function f
> (x,y)=x*y where x and y are equally evaluated between 0 and 1.
> When one uses the option drape=TRUE then each "square" between
the
> "wires" (lines that build the surface shape) gets a certain
color. A
> perfect wireframe plot of a continuous surface would be, if you
> (almost) can not distinguish between the colors of those
"squares"
> that lie adjacent to each other. So the idea would be, to choose many
> many evaluation points for x (and y), say x (and y) consists of 1000
> equally spaced intermediate points. But the problem is, that there
> are too many "wires" plotted... the whole picture is dark... On
the
> other hand, if you use only 20 points for the x (and also y) axis,
> then you get a really nice wired frame, but the colors for each
> "square" differ a lot (if you do not think that they differ a lot
> then just think of plotting a different function and this "color-
> problem" appears again). So the solution would be, to choose many
> many values for x (and y) _but_ only to plot wires -say- every 10th
> time, the color changes, i.e. not to plot _all_ wires but only a
> subset (every 10th wire for example). Is that possible?? How??
It is certainly possible, by making appropriate changes in
'panel.3dwire' (and wherever else that leads). I don't think it
would
be trivial, but R and lattice are Free Software, so you are welcome to
try.

You might alternatively consider using 'shade=TRUE', which allows
encoding of both height and orientation by color (rather than 'drape'
which encodes height by color and orientation by the `wires').

Deepayan
--
http://www.stat.wisc.edu/~deepayan/