[R] plotting order of lines in xyplot panels while using conditioning variable and groups

[Deepayan Sarkar]

On 6/19/07, RICHARD PITMAN <richard.pitman3 at btopenworld.com> wrote:
> I am using the following code:
>
> library(lattice)
> data<-read.csv("data.csv")
> attach(data)
>
> fig<-xyplot(S_t~month|event,
>        key    = list(text=list(lab=c("Time to first CV
> event - Data",
>                                      "Survival post
> first CV event - Model",
>                                      "Survival post
> first MIA/CA event - Data",
>                                      "Survival post
> first CVA event - Data",
>                                      "Survival post
> first TIA event - Data",
>                                      "Survival post
> first CVA/TIA event - Model"),
>                                font=2,
>                                cex=0.55),
>                      lines=list(col=c("red",
>                                       "magenta",
>                                       "blue",
>                                       "brown"),
>                                 type="l",
>                                 cex=0.55,
>                                 lwd=1.5,
>                                 pch=0:1),
>                      corner=c(0,0),x=0.75,y=0.75),
>        group  = group,
>        index.cond = list(c(4,5,6,7,1,2,3)),
>        type   = "l",
>        lwd    = "3",
>        ylim   = c(0,1.5),
>        layout = c(4,2),
>        col    = c("red","magenta","blue","brown"),
>        pch    = 0:3,
>        cex    = 0.5,
>        ylab   = "cumulative probability",
>        xlab   = "months",
>      )
> print(fig)
>
> However, in each panel, the order in which the lines
> are printed is suboptimal as some shorter lines are
> obscured under longer lines. I am having some trouble
> finding a method to change the order in which curves
> are plotted in each panel. I have tried reordering the
> levels in data$group:
>
> data$group<-factor(data$group,
> levels=c("CV_model_event_1","CV model event 2","CV
> event
> 1","CV_event_2","CV_event_2_CVA","CV_event_2_TIA"))
>
> but this changed nothing.
>
> Any suggestions gratefully received.

It's hard to see the problem without a reproducible example, but if
all you want is to order the levels of groups in decreasing order of
frequency, you could use

 groups  = reorder(group, group, function(x) { -length(x) }),

-Deepayan