[R] panel.axis() & grid/lattice settings

[Deepayan Sarkar]

On Wednesday 01 June 2005 05:43, Pikounis, Bill [CNTUS] wrote:
> Hello,
> I wish to customize the tick marks and labels of axes in panels produced by
> high-level lattice functions, namely xyplot. I know I can use the scales
> argument to specify values for rot, cex, etc. in the top-level call.
>
> However, I am interested in determining values for cex and rot based on the
> current panel / viewport and device. More specifically, I would like to
> make adjustments when tick labels overlap on the x-axis, such as labels of
> a factor. If I use base graphics, par("cin") or par("cxy") or strwidth(),
> etc. can be used to develop an algorithm to adjust cex or/and rot if
> needed.
>
> I am trying to determine the parameters/settings in grid analogous to
> par("cin"), etc. mentioned above, knowing that par() has no effect in
> lattice / grid. I have dug around the sources for grid and lattice but
> cannot seem to come up with such parameters -- most notably something like
> strwidth(). I see that panel.axis() has a check.overlap argument for
> labels, but I could not trace down the actual code to see how that works.
> What have I overlooked, or where should I be looking?

Paul may be able to give a more insightful answer, but grid allows a string to 
determine it's width in terms of itself, e.g.:

unit(1, "strwidth", data = "foo")

If you want to convert that into, say, inches, you could use 

> convertX(unit(1, "strwidth", data = "foo"), "inches", TRUE)
[1] 0.2344092

I think this would depend on the gpars() in effect, in particular fontsize.

> Indirectly related, setting outside=TRUE in a panel.axis() call does not
> produce visible labels, perhaps due to "issues of clipping" as mentioned in
> its help page. How might one disable clipping for the current panel /
> viewport?

At the grid level, there's a 'clip' argument to 'viewport()'. In lattice, 
these are chosen from 

> str(trellis.par.get("clip"))
List of 2
 $ panel: chr "on"
 $ strip: chr "on"

(In case you are using 'trellis.focus', that can set clipping off.)

Deepayan