[R] lattice: left-aligned text in strips?

[Charilaos Skiadas]

On May 15, 2008, at 3:18 AM, RINNER Heinrich wrote:

> Thanks for your help!
> I guess I could have thought for ages about this, and never would  
> such a solution have come to my mind ;-)
> It works as far as the text in the strips is left-aligned; a  
> remaining drawback is that printing of longer texts will be  
> continued outside the right border of their strip.

Yes, the only way to fix that I think will likely be to tell it to  
clip the string off, and to do that you would likely want to copy  
some of what strip.default does with viewports. Effectively, you need  
to create a new viewport occupying the strip space, and tell it to  
use clipping there. See the code for strip.default, and the  
pushViewport and upViewport calls. For example, using that code, this  
might work:

require(grid)
strip.left.aligned <- function(which.given, which.panel,  
factor.levels, ...) {
   pushViewport(viewport(y = (which.given - 0.5)/length(which.panel),
         height = 1/length(which.panel), clip = trellis.par.get 
("clip")$strip,
         name = paste("strip.default", which.given, sep = ".")))
    panel.rect(0, 0, 1, 1, col = trellis.par.get("strip.background") 
$col[which.given], border = 1)
    panel.text(x = 0, y = 0.5, pos = 4, lab = factor.levels 
[which.panel[which.given]])
    upViewport()
}
xyplot(y ~ x | a, data = test, strip = strip.left.aligned)

Haris Skiadas
Department of Mathematics and Computer Science
Hanover College


> For example, using your suggestion:
>
> ###
> library(lattice)
> test <- data.frame(x=rnorm(100), y=rnorm(100), a=rep(c("A", "B",  
> "C", "D: left-aligned text (possibly  
> looooooooooooooooooooooooooooooooooooooooong string"),25))
>
> strip.left.aligned <- function(which.given, which.panel,  
> factor.levels, ...) {
>    panel.rect(0, 0, 1, 1, col = trellis.par.get("strip.background") 
> $col[which.given], border = 1)
>    panel.text(x = 0, y = 0.5, pos = 4, lab = factor.levels 
> [which.panel[which.given]])
> }
>
> xyplot(y ~ x | a, data = test, strip = strip.left.aligned)
> ###
>
> Anywag, thanks again for having taken the time thinking about my  
> question;
> Heinrich.
>
>> -----Ursprüngliche Nachricht-----
>> Von: Charilaos Skiadas [mailto:cskiadas at gmail.com]
>> Gesendet: Mittwoch, 14. Mai 2008 13:30
>> An: RINNER Heinrich
>> Cc: r-help at stat.math.ethz.ch
>> Betreff: Re: [R] lattice: left-aligned text in strips?
>>
>>
>>
>> On May 14, 2008, at 3:47 AM, RINNER Heinrich wrote:
>>
>>> [adapted repost of question
>>> http://tolstoy.newcastle.edu.au/R/e4/help/08/03/6260.html]
>>>
>>> Dear R community,
>>>
>>> by default, text in the strips of a trellis plot is centered in the
>>> strip.
>>> Is there a way to have the text left-aligned?
>>>
>>> For example:
>>>
>>> library(lattice)
>>> test <- data.frame(x=rnorm(100), y=rnorm(100), a=rep(c("A: centered
>>> text","B: centered text"),50))
>>> xyplot(y ~ x | a, data = test)  # ok, strip text is centered
>>> test <- data.frame(x=rnorm(100), y=rnorm(100), a=rep(c("A: left-
>>> aligned
>>> text","B: left-aligned text (possibly
>> loooooooooooooooooooooooooooong
>>> string"),50))
>>> xyplot(y ~ x | a, data = test)  # how???
>>
>> Here's a way to do it, shamelessly stealing the main idea from:
>> http://dsarkar.fhcrc.org/lattice/book/figures.html?
>> chapter=10;figure=10_24
>>
>> Mainly you just have to write your own strip function.
>>
>> xyplot(Petal.Length~Petal.Width|Species, iris, strip=function
>> (which.given,which.panel, factor.levels,...) {
>>    panel.rect(0, 0, 1, 1, col = trellis.par.get("strip.background")
>> $col[which.given], border = 1)
>>    panel.text(x = 0, y = 0.5, pos = 4, lab =
>> factor.levels[which.panel
>> [which.given]])
>> } )
>>
>> Better yet, you should probably write a more generic strip function
>> that does what you want.
>>
>> I would however consider using ?abbreviate for what you want to do
>> instead.
>>
>>> I am using R 2.6.2 on Windows XP, package lattice Version 0.17-6.
>>>
>>> [The reason I would like to do this is because "in real life" my
>>> conditioning variable 'a' can have quite long strings as
>> its value.
>>> I am
>>> automatically creating a series of trellis plots, and in each one a
>>> different number of panels will be produced (maybe 4, maybe
>>> 20,...). So
>>> in some cases (few panels, short labels) text in the strips will be
>>> perfectly readable, while in some cases (many panels, long labels)
>>> only
>>> the middle of the text will.
>>> I know I could abbreviate the strip text by using something like:
>>> xyplot(y ~ x | substr(a,1,35), data = test)
>>> But there is no "natural" choice of string length here when
>> I want to
>>> cut off as few text as possible, so just left aligning the
>> strip texts
>>> would seem like a natural and easy(?) solution to me - if I was
>>> able to
>>> do it...]
>>>
>>> -Heinrich.
>>
>> Haris Skiadas
>> Department of Mathematics and Computer Science
>> Hanover College
>>
>>
>>
>>
>>