[R] Putting regression lines on SPLOM

(Ted Harding) Ted.Harding at nessie.mcc.ac.uk
Fri Sep 5 20:18:31 CEST 2003

Hi Deepayan,
Thanks again, especially for the careful explanation. Some comments
(in snipped context) below:

On 05-Sep-03 Deepayan Sarkar wrote:
> On Friday 05 September 2003 10:04 am, Ted Harding wrote:
>> Another query:
>> I'm now trying to have the x- and y-axes all on the same scale
>> (0:15) in every panel, whereas the default behaviour of splom
>> is to scale them according to the ranges of the individual
>> variables in each panel.
>> [...]
> [...]
> Unfortunately, the current implementation of splom (in particular the 
> panel.pairs function) does not allow you to do what you want in any
> other way either (however, read on for a solution).
> [...]
> ... This feature was missing till now, but I have added something for
> the next release (source() the attached file to use it), which will
allow you to do:
> splom(log(1+DF),
>       prepanel.limits = function(x) c(0, 15),
>       panel = function(x, y, ... ) {
>           panel.xyplot(x, y, ...)
>       })

*** No file was attached  :((

> [...]
>> ?panel.xyplot refers you to ?xyplot for "further arguments",
>> and ?xyplot certainly specifies the above form for specifying
>> x- and y-limits. I think ...
> Where exactly does it do that ? xyplot is in the "See Also" section,
> but how does that imply that arguments accepted by xyplot can be
> given to panel.xyplot ? And I don't see the phrase "further
> arguments" anywhere in the help page for panel.xyplot.
> If there's anything in the documentation that even suggests that xlim
> and ylim can be passed to panel functions, that's definitely
> misleading, and I would appreciate it if you could point out any such
> confusing statements.

Quite possible I was not reading sufficiently between the lines,
but the indications that led me down that path come from the following

  ?splom -> ?panel.xyplot ->

  panel.xyplot      package:lattice      R Documentation
  Default Panel Function for xyplot
       This is the default panel function for `xyplot'.
       panel.xyplot(x, y, type="p",
       lwd = plot.line$lwd, ...)
       ...: other arguments, e.g., arguments to pass to `panel.loess'.
  See Also:
       `panel.superpose', `xyplot', `splom',`qqmath'

and of course ?xyplot leads to the 'xlim' and 'ylim' parameters.

I guess the expectation was that "e.g." in the "other arguments" line
permitted the hypothesis that since controlling axis scales would 
probably be a common need and so there might be a mechanism for it
(but not mentioned so far down the path), the natural next direction
to try was the suggested "see xyplot" where what looks like a mechanism
can be found.

I agree, though, that the above does not logically imply that this is
indeed such a mechanism: it merely creates an expectation (albeit in
my case quite a strong one) that it would be; and some resulting
surpise that it did not work! So I guess this falls within your
"even suggests", even though it's not overtly misleading.

Anyway, many thanks again for the elucidations, and I look forward
to receiving the file to try the new feature!

Best wishes,

E-Mail: (Ted Harding) <Ted.Harding at nessie.mcc.ac.uk>
Fax-to-email: +44 (0)870 167 1972
Date: 05-Sep-03                                       Time: 19:18:31
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