R help - Feb 2004 - levelplot add line

R folks,

I can't seem to find the instructions in the help files for the lattice 
package that explain how to add lines, such as with lines() or ?, to a 
levelplot.  I'd be grateful if someone could point me in the proper
direction.

Cheers,

Jeff

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Jeff Jorgensen

Center for Limnology                             jcjorgensen at wisc.edu
University of Wisconsin Madison           ph (608) 263-2304
680 North Park Street                           fx (608) 265-2340
Madison, Wisconsin 53706                http://limnology.wisc.edu

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

On Tuesday 24 February 2004 18:03, Jeff Jorgensen wrote:
> R folks,
>
> I can't seem to find the instructions in the help files for the lattice
> package that explain how to add lines, such as with lines() or ?, to a
> levelplot.  I'd be grateful if someone could point me in the proper
> direction.
The general rule for all lattice functions is to write your own panel 
function. For example, 

data(volcano)
levelplot(volcano, 
          panel = function(...) {
              panel.levelplot(...)
              panel.abline(c(0,1))
          })

lines() will not work for lattice, but you can use llines() instead. 

Of course, for anything more useful than this example, your panel function 
should make use of the data that's passed to the panel function. Exactly 
what would be passed depends on the function in question. For levelplot, 
the best place to look will be panel.levelplot, and similarly for other 
functions.

Hth,

Deepayan

Deepayan,

Thanks for the quick response.  Just to make sure I understand, let me 
explain in a bit more detail what I am trying to do.

I have created a levelplot (with contour lines and colored regions), and 
what I am trying to figure out now is how to add a series of horizontal 
lines across the levelplot and also assign values or labels to the lines on 
the alternative y-axis.  Would I do this with the route you suggest below?


Thanks so much for the help,

Jeff


At 06:51 PM 2/24/2004 -0600, you wrote:
>On Tuesday 24 February 2004 18:03, Jeff Jorgensen wrote:
> > R folks,
> >
> > I can't seem to find the instructions in the help files for the
lattice
> > package that explain how to add lines, such as with lines() or ?, to a
> > levelplot.  I'd be grateful if someone could point me in the
proper
> > direction.
>
>The general rule for all lattice functions is to write your own panel
>function. For example,
>
>data(volcano)
>levelplot(volcano,
>           panel = function(...) {
>               panel.levelplot(...)
>               panel.abline(c(0,1))
>           })
>
>lines() will not work for lattice, but you can use llines() instead.
>
>Of course, for anything more useful than this example, your panel function
>should make use of the data that's passed to the panel function. Exactly
>what would be passed depends on the function in question. For levelplot,
>the best place to look will be panel.levelplot, and similarly for other
>functions.
>
>Hth,
>
>Deepayan