Re: [R] RGui: windows-record and command history

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Re: [R] RGui: windows-record and command history

Duncan Murdoch
I've moved this from r-help to r-devel.

On 3/23/2006 8:17 PM, Paul Murrell wrote:

>>
>> Paul,
>> If I read your comments correctly, the problem with manipulating the
>> graph history is with saved histories across sessions/versions. Is
>> there any reason not to manipulate it *within* a session? I never
>> save plots for re-use in R. Re-running code is usually best for me.
>> But I would find it handy to fiddle with the display list in a
>> session.
>
>
> That is *one* problem with the display list.  Messing directly with the
> display list *within a session* is *less* dangerous, but R's behaviour
> if you do that is "undefined".
>
> The display list is technically an internal structure for R's internal
> use.  We can't stop you playing with it, but I do not encourage it and
> it is not officially supported.
>
> There are a number of simple things that you could do to the display
> list that should work, but providing proper support for general
> manipulations of the display list would require a significant amount of
> (re)design of the R graphics code.
>
> Paul
>
> p.s.  These comments apply to the display list in R's "graphics engine".
>   The 'grid' package also maintains a display list, and that has been
> designed to support more general manipulations.

Are we talking about the same thing?  I think Peter is only thinking of
manipulating the .SavedPlots variable, which is a Windows-only object
holding plot history.  I imagine the entries in .SavedPlots[[5]] are the
things that you are worried about, and I agree people shouldn't play
with those, they should be using grid instead with its documented interface.

If we do warn people off manipulating .SavedPlots, then I think it
should be a higher priority to implement some manipulations ourselves,
e.g. "[<-.SavedPlots", to allow entries to be moved around or deleted in
the list.

Duncan

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Re: [R] RGui: windows-record and command history

Paul Murrell
Hi


Duncan Murdoch wrote:

> I've moved this from r-help to r-devel.
>
> On 3/23/2006 8:17 PM, Paul Murrell wrote:
>
>>>
>>> Paul,
>>> If I read your comments correctly, the problem with manipulating the
>>> graph history is with saved histories across sessions/versions. Is
>>> there any reason not to manipulate it *within* a session? I never
>>> save plots for re-use in R. Re-running code is usually best for me.
>>> But I would find it handy to fiddle with the display list in a
>>> session.
>>
>>
>>
>> That is *one* problem with the display list.  Messing directly with
>> the display list *within a session* is *less* dangerous, but R's
>> behaviour if you do that is "undefined".
>>
>> The display list is technically an internal structure for R's internal
>> use.  We can't stop you playing with it, but I do not encourage it and
>> it is not officially supported.
>>
>> There are a number of simple things that you could do to the display
>> list that should work, but providing proper support for general
>> manipulations of the display list would require a significant amount
>> of (re)design of the R graphics code.
>>
>> Paul
>>
>> p.s.  These comments apply to the display list in R's "graphics
>> engine".   The 'grid' package also maintains a display list, and that
>> has been designed to support more general manipulations.
>
>
> Are we talking about the same thing?  I think Peter is only thinking of
> manipulating the .SavedPlots variable, which is a Windows-only object
> holding plot history.  I imagine the entries in .SavedPlots[[5]] are the
> things that you are worried about, and I agree people shouldn't play
> with those, they should be using grid instead with its documented
> interface.


Sorry, I came into the discussion a bit late, so there's a good chance I
have misunderstood.  Within a session, manipulation of .SavedPlots (via
the appropriate interface) seems reasonable (i.e., manipulations
involving an entire "page" of output as the basic unit).  Warnings about
use *between* sessions still apply though.

Paul


> If we do warn people off manipulating .SavedPlots, then I think it
> should be a higher priority to implement some manipulations ourselves,
> e.g. "[<-.SavedPlots", to allow entries to be moved around or deleted in
> the list.
>
> Duncan

--
Dr Paul Murrell
Department of Statistics
The University of Auckland
Private Bag 92019
Auckland
New Zealand
64 9 3737599 x85392
[hidden email]
http://www.stat.auckland.ac.nz/~paul/

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