[R] adding text to the top corner of a lattice plot

[Gabor Grothendieck]

On Fri, Dec 17, 2010 at 6:57 AM, Gabor Grothendieck
<ggrothendieck at gmail.com> wrote:
> On Fri, Dec 17, 2010 at 12:07 AM, Rajarshi Guha <rajarshi.guha at gmail.com> wrote:
>> On Thu, Dec 16, 2010 at 11:26 PM, David Winsemius
>> <dwinsemius at comcast.net> wrote:
>>>
>>> On Dec 16, 2010, at 11:12 PM, Rajarshi Guha wrote:
>>>
>>>> Hi, I have a series of lattice plots which I am arranging in a 2x2
>>>> grid via print:
>>>>
>>>> print(p.preds, split=c(1,1, 2,2), more=TRUE)
>>>> print(p.comp, split=c(2,1,2,2), more=TRUE)
>>>> print(p.bw, split=c(1,2,2,2), more=FALSE)
>>>>
>>>> What I'd like to have is a letter (A, B, ...) in the top corner of
>>>> each plot. While panel.text lets me add text anywhere within a plot, I
>>>> can't seem to workout how I could put some text in the top left
>>>> corner, say, of the whole plotting region.
>>> ########>>>>>>>>>
>>>>
>>>> and provide commented, minimal, self-contained, reproducible code.
>>
>> Apologies for an incomplete post. Example code, based on Gabors suggestion is
>>
>> library(gridExtra)
>> p1 <- xyplot(demand ~ Time, BOD)
>> p2 <- xyplot(demand ~ Time, BOD)
>> p3 <- xyplot(demand ~ Time, BOD)
>> print(p1, split=c(1,1,2,2), more=TRUE)
>> print(p2, split=c(2,1,2,2), more=TRUE)
>> print(p3, split=c(1,2,2,2), more=FALSE)
>>
>> However, Gabors approach places the mark within the plot itself. What
>> I'd ideally like is to have the mark be located in the margins, in the
>> top right corner. (I am not sure of the correct terminology here). An
>> example of the desired output can be seen at
>> http://rguha.net/plot-annot.png
>
> In that case use page= rather than panel=.   Unfortunately page only
> passes the page number but we can wrap it in a proto object from the
> proto package to get the desired effect:
>
> library(gridExtra)
> library(proto)
> pg <- function(., n) grid.text(label = mark,
>        just = c("left", "center"),
>    x = unit(0.1, "npc"), y = unit(0.9, "npc"))
> fo <- demand ~ Time
> grid.arrange(nrow = 2,
>        xyplot(fo, BOD, page = proto(mark = "A", pg = pg)$pg),
>        xyplot(fo, BOD, page = proto(mark = "B", pg = pg)$pg),
>        xyplot(fo, BOD, page = proto(mark = "C", pg = pg)$pg)
> )

and here is a solution not using proto.  Instead of the pg function we
have pgfun which generates a page function rather than being the page
function:

library(gridExtra)
pgfun <- function(mark) function(n) grid.text(label = mark,
	just = c("left", "center"),
    x = unit(0.1, "npc"), y = unit(0.9, "npc"))
fo <- demand ~ Time
grid.arrange(nrow = 2,
	xyplot(fo, BOD, page = pgfun("A")),
	xyplot(fo, BOD, page = pgfun("B")),
	xyplot(fo, BOD, page = pgfun("C"))
)


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