[R] customizing the color and point shape for each line drawn using lattice's xyplot

[deepayan.sarkar at gmail.com]

On 8/29/07, Gen <gingerlygen at gmail.com> wrote:
>
> Description of what I am trying to do:
> I am using the xyplot code below to plot the variable "MeanBxg" against the
> variable "PercentVarExplained" for all 9 possible combinations of variables
> "bdg" and "bdx".  Within each of these 9 scenarios I am plotting a separate
> line for each of up to 9 different methods that I used to estimate the
> variable MeanBxg. These methods are identified by the numeric variable
> called "Method."  Giving me one plot with 9 figures and each of the figures
> contains 9 lines.
>
> My problem arises because I would like to repeat the creation of this plot 8
> times, in each instance only a subset (eg 6) of the 9 methods are used (a
> different subset each time).
>
> What I can't figure out:
> I would like to learn how to specify the exact line color that corresponds
> to each method such that Method==1 will always be represented by the same
> color (in every plot that it appears in).  Where two methods that I used
> were of the same family of methods (say method==1 and method==2 made the
> same assumptions about the data)  I would like to, if possible, represent
> the two methods using the same color and distinguish them by the symbol used
> to represent points on the line.
>
> My code as it currently stands:
> xyplot(MeanBxg ~ PercentVarExplained | bdg.f * bdx.f, data=common,
> groups=common$Method.f, type="l", subset= Method!=4, auto.key=T)
>
> As the code is, the default colors assigned are repeated causing different
> methods to be represented by the same color with no way to distinguish them
> (I have not succeeded in plotting lines and points simultaneously).
>
> Side question: When I subset the data to particular methods, is there a way
> to remove the excluded methods from the key as well? (in my code "Method" is
> a numeric variable, and "Method.f" corresponds to the lengthy descriptions
> of each method for the purpose of the key)


It's not clear what you actually want, and you haven't given us a
reproducible example. Some general comments:

1. try type = "o" for both points and lines, and auto.key =
list(points = TRUE, lines = TRUE) if you meant this for the legend.

2. The number of distinct colors is 7 by default, after which they get
recycled. You can set the colors by changing the superpose.line$col
setting (see ?trellis.par.set and the entry for 'par.settings' in
?xyplot)

3. The number of colors used is related to the number of levels of
'groups'. If you want fewer colors (or not have unused colors in the
legend), you need to make sure your 'groups' variable has a suitably
reduced set of levels. There is no cute way to do this. The long way
is

subdata <- subset(common, Method != 4)
subdata$Method.f <- subdata$Method.f[, drop = TRUE]

-Deepayan