[R] Retrieving x argument name from a trellis object

[Deepayan Sarkar]

On Fri, Aug 14, 2009 at 11:04 AM, <vincenzo.2.di-iorio at gsk.com> wrote:
>
> Dear Deepayan,
>
> First of all I'm sorry for resuming such an old thread, but I think I may
> have found an easy fix.
>
> Replacing in "xyplot.formula" (and similar internal functions for the other
> Trellis plots)
>
>     foo$call <- sys.call(sys.parent())
>     foo$call[[1]] <- quote(xyplot)
>
> with
>
>     foo$call <- match.call()
>     foo$call[[1]] <- quote(xyplot)
>
> will restore the correct behaviour while keeping the new better value for
> the call component of a trellis object introduced in lattice version 0.16 or
> higher, that if I understand correctly depends on the second (unchanged)
> line.

But consider this: we currently get

> vad <- as.table(VADeaths)
> summary(barchart(vad))

Call:
barchart(vad)

Number of observations:
[1] 20


> summary(barchart(VADeaths))

Call:
barchart(as.table(x), data, ...)

Number of observations:
[1] 20

Not perfect, but not too bad either, considering that neither
barchart.matrix() nor barchart.table() do any manipulation of the
$call component.

If I make your suggested change in barchart.formula, this is what I get:

> summary(barchart(VADeaths))

Call:
barchart(x = as.formula(form), data = data, groups = eval(groups),
    origin = origin, stack = stack)

Number of observations:
[1] 20


Which would you rather have?


The point remains that the call component is meant for cosmetic use.
If you can convince me that having the other form is important, I will
be happy to include it in the "trellis" object (under a different
name, perhaps "mcall").

-Deepayan

>
> Best regards
> Vincenzo
>
> -----------------------------------------------------------------------------------
> Vincenzo Luca Di Iorio
> Consultant PME User support - GSK R&D Limited
> -----------------------------------------------------------------------------------
>
>
>
> "Deepayan Sarkar" <deepayan.sarkar at gmail.com>
>
> 12-Nov-2008 07:04
>
>
> To
> "vincenzo.2.di-iorio at gsk.com" <vincenzo.2.di-iorio at gsk.com>
> cc
> "R help" <R-help at stat.math.ethz.ch>
> Subject
> Re: [R] Retrieving x argument name from a trellis object in R 2.8.0
>
>
>
>
> On 11/11/08, vincenzo.2.di-iorio at gsk.com <vincenzo.2.di-iorio at gsk.com>
> wrote:
>> Dear all,
>>
>>  let consider the following function:
>>
>>  Fun1 <- function() {
>>   library(lattice)
>>   plot1 <- 1:10~1:10
>>   pl1 <- xyplot(plot1)
>>   return(pl1$call$x)
>>  }
>>
>>  In R 2.5.0 (or older version) we have
>>
>>  > Fun1()
>>  plot1
>>
>>  but starting from R 2.5.1 until the latest R 2.8.0  we obtain instead
>>
>>  > Fun1()
>>  NULL
>>
>>  because pl1$call seems to be equal to xyplot() without arguments.
>>
>>  Something like xyplot(x=plot1) doesn?t work either. Again we have that
>>  pl1$call is equal to xyplot() without arguments
>>
>>  The situation is slightly different if we call the xyplot in the global
>>  environment:
>>
>>  > plot1 <- 1:10~1:10
>>  > pl1 <- xyplot(plot1)
>>  > pl2 <- xyplot(x=plot1)
>>
>>  then we have
>>
>>  > pl1$call
>>  xyplot(plot1)
>>  > pl1$call$x
>>  NULL
>>
>>  but at least
>>
>>  > pl2$call
>>  xyplot(x = plot1)
>>  > pl2$call$x
>>  plot1
>
> This is what I would have expected.
>
> I'm surprised at the odd behaviour when xyplot() is called inside a
> function, which is probably caused by my lack of understanding of how
> sys.call() works. However, the 'call' component is provided mainly for
> cosmetic reasons, and was never intended to be used programmatically.
> Why do you need this?
>
> -Deepayan
>
>>  Someone knows if in R 2.8.0 it is possible to retrieve the name of the x
>>  argument (i.e. plot1) directly from an object of class ?trellis? when the
>>  corresponding lattice function (e.g. xyplot) is inside another function
>>  (e.g. Fun1)?
>>
>>  Thanks in advance
>>  Vincenzo
>>
>>
>>  -----------------------------------------------------------------------------------
>>  Vincenzo Luca Di Iorio
>>  Consultant PME User support - GSK R&D Limited
>>
>>  -----------------------------------------------------------------------------------
>>
>>         [[alternative HTML version deleted]]
>>
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>>
>
>
>