[R] [FORGED] Extracting specified pages from a lattice ("trellis") object.

[Paul Murrell]

Hi

I think the subsetting works by giving you the panels for the 
corresponding levels of the conditioning variable(s).  Note that, if 
there is more than one conditioning variable, you will need more than 
one subsetting index.

For example, taking this plot with two conditioning variables and 12 
panels in total ...

dotplot(variety ~ yield | year * site, data=barley)

... this produces three pages ...

dotplot(variety ~ yield | year * site, data=barley,
         layout=c(2,2))

... and this produces the second page (both panels for the first 
conditioning variable and the third and fourth panels for the second 
conditioning variable) ...

dotplot(variety ~ yield | year * site, data=barley,
         layout=c(2,2))[1:2, 3:4]

Hope that helps

Paul

On 14/04/18 12:25, Rolf Turner wrote:
> 
> Suppose that (e.g.) xyplot() returns an object "xxx" with (say) 3 pages.
> I would like to extract/plot (print) just one of these pages, e.g.
> page 2.
> 
> Here's a toy example:
> 
> x   <- rep(seq(0,1,length=11),12)
> set.seed(42)
> y   <- rnorm(3*44)
> a   <- rep(letters[1:12],each=11)
> dta <- data.frame(x=x,y=y,a=a)
> xxx <- xyplot(y~x|a,data=dta,layout=c(2,2))
> 
> I would to extract from xxx and print page 2 (the page corresponding to
> levels e, f, g and h).
> 
> Is there any (simple) way that I can do this?
> 
> I've mucked around with update.trellis() and [.trellis, but I cannot 
> make head nor tail of the documentation.  The [.trellis method seems to 
> work in some situations, but not in others, and since I cannot 
> understand what it actually does, I cannot figure out why.
> 
> E.g. in my toy example "xxx[5:8]" seems to give me what I want, but in 
> the context of my real application a similar construction does not work.
> 
> Thanks for any insight.
> 
> cheers,
> 
> Rolf Turner
> 

-- 
Dr Paul Murrell
Department of Statistics
The University of Auckland
Private Bag 92019
Auckland
New Zealand
64 9 3737599 x85392
paul using stat.auckland.ac.nz
http://www.stat.auckland.ac.nz/~paul/