On May 25, 2011, at 5:56 PM, Gene Leynes wrote:
David, Peter (and others),
If you're interested, I submitted this as a bug, and was informed of
the error of my ways by Professor Ripley
* His informative reply is copied below. *
The short answer is that panel.first is not a documented function of
"plot.formula", which is called by the generic "plot".
Apparently not the first time he has been called upon to do so. Here
is a similar question, albeit with no answer (at least in Baron's
archive) at that time.
http://finzi.psych.upenn.edu/Rhelp10/2009-September/210328.html
(... the link to the ancient bug is broken.)
But plot.formula promises to pass "..." arguments to later "hand
offs" and apparently it munges up the 'dots' in a manner that
plot.data.frame does not. In fact, plot.formula gets handed back to
generic `plot`. Prof Ripley obviously has an understanding of the term
`expression` that surpasses mine. Does your understaning of his reply
extend to explaining why plot.data.frame works with our naive
invocation of panel.first while his suggested syntax does not:
plot(dat, panel.first=quote( bgfun() ) ) # Fails.
plot(dat, panel.first= bgfun() ) # Succeeds.
So I it still appears there is a demonstrable degree of inconsistency,
even if there is no "bug".
The solution gives me some insight into how the lazy evaluation works.
## Note: It's still not a documented use of the function!
plot(y ~ x, data=dat, panel.first=quote(bgfun()))
On Wed, May 25, 2011 at 2:13 AM, <r-b...@r-project.org> wrote:
https://bugs.r-project.org/bugzilla3/show_bug.cgi?id=14591
Brian Ripley <rip...@stats.ox.ac.uk> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |CLOSED
Resolution| |INVALID
--- Comment #1 from Brian Ripley <rip...@stats.ox.ac.uk> 2011-05-25
03:13:34 EDT ---
panel.first is not a documented argument to plot.formula: please do
read the help.
Yes, I did read the help page. I also looked at the code (of
plot.formula, plot.data.frame, and plot.default) and made a good
faith effort at following the flow of data through that code by
inserting print and str statements at what appeared to be critical
points so I could see where plot.formula was "going" and what it was
being given to work with.
It is a documented argument to plot.default(), as
panel.first: an expression to be evaluated after the plot axes are set
^^^^^^^^^^
but you passed an evaluated function call. It first ran bgfun() and
then the
plot call. It worked for plot.default() by lazy evaluation.
I also tried using just panel.first=bgfun as I would have with lattice
calls, and it did not succeed in any application.
You needed
plot(y ~ x, data=dat, panel.first=quote(bgfun()))
--
David Winsemius, MD
West Hartford, CT
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