coloring individual points in lattice xyplot

On 7/5/06, Gabor Grothendieck <ggrothendieck at gmail.com> wrote:

On 7/5/06, Deepayan Sarkar <deepayan.sarkar at gmail.com> wrote:

On 7/4/06, Gabor Grothendieck <ggrothendieck at gmail.com> wrote:

OK.  It looks like I need to go to the lower level llines and lpoints to
do this.  I wrote a panel routine, mypanel, and it seems to work (see
below); however, currently it assumes types and cols are in the global
environment or at least somewhere where they will be found.

1. Is it somehow possible to stick these into some structures set up by
lattice already and then retrieve them from lattice from within mypanel?

Not sure what you mean by that, but I would do something like the
following (this allows 'col' to be a list as in your original post).
Note that arguments to the panel function can be supplied directly to
the high level function (that's why graphical parameters can be
supplied to xyplot in the first place).

mypanel <-
   function(x, y, subscripts, groups,
            col = 1,
            type = "p",
            ...)
{
   col <- rep(as.list(col), length = nlevels(groups))
   type <- rep(as.list(type), length = nlevels(groups))
   for(g in 1:nlevels(groups)) {
        idx <- g == groups[subscripts]
        xx <- x[idx]; yy <- y[idx];
        panel.xyplot(x[idx], y[idx],
                     col = col[[g]],
                     type = type[[g]],
                     ...)
   }
}

xyplot(y ~ c(x,x), groups = factor(col(y)),
      panel = mypanel,
      type = c("o", "p"),
      col = list("black", 1:10))

Thanks!!! This is quite an improvement.

2. Any other improvements to the example below?

mypanel <- function(x, y, subscripts, groups, ...) {
      for(g in 1:nlevels(groups)) {
         idx <- g == groups

This won't work for more than one panel.

Could you explain this?  Under what situation does it not work?
The following, for example, appears to work:

xyplot(y ~ c(x,x) | col(y), groups = factor(col(y)),
     panel = mypanel,
     type = c("o", "p"),
     col = list("black", 1:10),
     layout = 1:2)

Just to clarify mypanel refers to your version of mypanel.
Were you saying that your version still does not work in certain
situations with multiple panels or only mine?