[R] Auto.key colors maintained when subsetting

[Deepayan Sarkar]

On 7/9/08, David Afshartous <dafshartous at med.miami.edu> wrote:
>
>
>
>  On 7/9/08 1:07 PM, "Deepayan Sarkar" <deepayan.sarkar at gmail.com> wrote:
>
>  > On 7/9/08, David Afshartous <dafshartous at med.miami.edu> wrote:
>  >>
>  >>
>  >>  All,
>  >>
>  >>  I'm plotting points and lines for various groups.
>  >>  I'd like subsequent plots done on subsets to maintain the color assignments
>  >>  from the original plot.  This works fine, but the key for the subset doesn't
>  >>  maintain the correspondence.  One solution is to reprint the entire key, but
>  >>  this is undesirable since then the key has more elements than the groups in
>  >>  the plot.  Reproducible example below.
>  >
>  > Well, the ideal solution would have been for auto.key to magically
>  > omit the levels of 'groups' that are omitted by the application of
>  > 'subset', but there is not enough information available to it for this
>  > to happen. One option is to
>  >
>  > 1. subset the data beforehand, and drop unsed levels with Group[drop=TRUE]
>
> This will work, but unfortunately the color correspondence across plots will
>  be lost.  Leading to a preference for your second suggestion:

I meant both 1 and 2 together...but in any case, the other option is
easier, I think.

>  > 2. supply colors, etc. explicitly through 'par.settings'.
>
> The code below works, but when extended to include error bars (panel.ci, and
>  prepanel.ci), it works for the full data but not the subset.

[...]

>  > The other option is to construct your own key (i.e., use the 'key'
>  > argument, not 'auto.key', to specify the legend).
>
> Below is an attempt to use key; although the plot is correct, in the key the
>  color is applied to the text instead of the line and the line type isn't
>  drawn:
>
>
>  xyplot(Y ~ Hour,
>         data = dat, pch = 16,
>         subset = (Group != "A"),
>
>         groups=Group, col=c('red', 'black', 'green', 'blue'),
>         type="b",
>         key = simpleKey(text = levels(Group)[2:4], lty = c(2,3,4),
>              space = "top", columns = 3, points = FALSE, lines = TRUE,
>              col = c('black', 'green', 'blue'))
>         par.settings = list(superpose.line = list(lty = c(1,2,3,4),
>          col=c('red', 'black', 'green', 'blue')
>  ) ) )

simpleKey() won't be of much help; I meant the use of a manually
constructed 'key', e.g.:


all.colors <- c('red', 'black', 'green', 'blue')
lgroups <- levels(dat$Group)

skip <- 1 ## or skip <- 2, skip <- c(1, 2), etc.

xyplot(Y ~ Hour, data = dat, groups = Group,
       subset = (Group %in% lgroups[-skip]),
       type = "b",
       pch = 16, col = all.colors,
       key = list(space = "top", columns = 3,
                  text = list(lgroups[-skip]),
                  lines = list(col = all.colors[-skip])))

-Deepayan

>  #############################
>  Data and necessary functions:
>  set.seed(101)
>
> Y = c(rnorm(4,0), rnorm(4,2), rnorm(4,6), rnorm(4,8))
>
> dat = data.frame(
>     Y , lower.bound = Y - .5, upper.bound = Y + .5,
>
>     Group = factor(c(rep("A", 4), rep("B", 4), rep("C", 4), rep("D", 4))),
>
>  Hour = rep(c(1:4), 4)
>  )
>
> prepanel.ci <- function(x, y, ly, uy, subscripts, ...) {
>     x <- as.numeric(x)
>     ly <- as.numeric(ly[subscripts])
>     uy <- as.numeric(uy[subscripts])
>     list(ylim = range(y, uy, ly, finite = TRUE)) }
>  panel.ci <- function(x, y, ly, uy, subscripts, pch = 16, ...) {
>     x <- as.numeric(x)
>     y <- as.numeric(y)
>     ly <- as.numeric(ly[subscripts])
>     uy <- as.numeric(uy[subscripts])
>     panel.arrows(x, ly, x, uy, col = "black",
>                  length = 0.25, unit = "native",
>                  angle = 90, code = 3)
>     panel.xyplot(x, y, pch = 16, ...)}
>
>  > It should be simple
>  > to write a function that constructs a suitable 'key' argument given
>  > the levels that are to be omitted/retained.
>  >
>  > -Deepayan
>
>