R help - Nov 2013 - Finding absolute viewport location in grid / lattice

I'm trying to do some post-plot manipulation of some lattice graphics, in
which I need to get the absolute viewport locations on the plotting device. So
for example:

library(lattice)
print(xyplot(Petal.Length ~ Sepal.Length | Species, iris, layout = c(2, 2)))
trellis.focus('panel', 1, 1)

This shows the item I want to identify. I need to know, for example, that the
lower left corner of the highlighted panel is at (0.1, 0.1) of the plotting
device. Hopefully there's some grid shenanigans I can use to do so.

To put the question into context (in case there's an alternative way):
I'm constructing PDF reports that are an amalgam of PDF figures, constructed
through LaTeX programmatically constructed in R, and I'd like to be able to
add tooltips to some of the data points on the graphs. To do so, I'm
overlaying a tikz (empty) image that uses the pdfcomment package to add the
tooltips. Hence I need to be able to calculate where some of the points are on
the screen so I can calculate where to put the tooltip 'hit-zones'. This
would be fairly trivial using javascript / actionscript and mouseover hooks, but
I'm constrained by PDF.

Thanks,
Jim Price.
Strength in Numbers.

 		 	   		  
	[[alternative HTML version deleted]]

Hi

Take a look at current.transform() (the grid.locator() function shows an 
example use)

Paul

On 11/06/13 13:35, James Price wrote:
> I'm trying to do some post-plot manipulation of some lattice
> graphics, in which I need to get the absolute viewport locations on
> the plotting device. So for example:
>
> library(lattice) print(xyplot(Petal.Length ~ Sepal.Length | Species,
> iris, layout = c(2, 2))) trellis.focus('panel', 1, 1)
>
> This shows the item I want to identify. I need to know, for example,
> that the lower left corner of the highlighted panel is at (0.1, 0.1)
> of the plotting device. Hopefully there's some grid shenanigans I can
> use to do so.
>
> To put the question into context (in case there's an alternative
> way): I'm constructing PDF reports that are an amalgam of PDF
> figures, constructed through LaTeX programmatically constructed in R,
> and I'd like to be able to add tooltips to some of the data points on
> the graphs. To do so, I'm overlaying a tikz (empty) image that uses
> the pdfcomment package to add the tooltips. Hence I need to be able
> to calculate where some of the points are on the screen so I can
> calculate where to put the tooltip 'hit-zones'. This would be
fairly
> trivial using javascript / actionscript and mouseover hooks, but I'm
> constrained by PDF.
>
> Thanks, Jim Price. Strength in Numbers.
>
>  [[alternative HTML version deleted]]
>
> ______________________________________________ R-help at r-project.org
> mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do
> read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
-- 
Dr Paul Murrell
Department of Statistics
The University of Auckland
Private Bag 92019
Auckland
New Zealand
64 9 3737599 x85392
paul at stat.auckland.ac.nz
http://www.stat.auckland.ac.nz/~paul/