[R] panel.rect and log scale in lattice plot

Garbade, Sven Sven@G@rb@de @end|ng |rom med@un|-he|de|berg@de
Wed Mar 23 13:32:05 CET 2022

using trellis.last.object()$y.scales$log helps a lot, thanks! I now check whether data were transformed and apply an appropriate transformation if needed. Maybe it helps when current.panel.limit() has information about transformations, so someone doesn't need to call 'trellis.last.object()', too.

Von: Deepayan Sarkar <deepayan.sarkar using gmail.com>
Gesendet: Mittwoch, 23. März 2022 12:05
An: Ivan Krylov
Cc: Garbade, Sven via R-help; Garbade, Sven
Betreff: Re: [R] panel.rect and log scale in lattice plot

On Wed, Mar 23, 2022 at 4:08 PM Ivan Krylov <krylov.r00t using gmail.com> wrote:
> On Wed, 23 Mar 2022 09:38:34 +0000
> "Garbade, Sven via R-help" <r-help using r-project.org> wrote:
> >            cpl <- current.panel.limits()
> If you str() the return value of current.panel.limits() from the panel
> function with log-scaling enabled, you can see that it contains the
> logarithm of the y-values, as do the y values themselves. This is
> consistent with ?xyplot saying:
> >> Note that this is in reality a transformation of the data, not the
> >> axes. Other than the axis labeling, using this feature is no
> >> different than transforming the data in the formula; e.g.,
> >> ‘scales=list(x = list(log = 2))’ is equivalent to ‘y ~ log2(x)’.
> ...although it could be more explicit.
> If you take a logarithm of 10 and 500, lrect() should be able to
> produce a rectangle in the right place.

Right, "log scales" in lattice simply transform the data, unlike in
traditional graphics.

If it helps, I could change current.panel.limits() to return
information on whether the data were transformed. For now, a
roundabout way to detect this inside the panel function is to use
trellis.last.object()$y.scales$log etc.


> --
> Best regards,
> Ivan
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