[R] features of save and save.image (unexpected file sizes)

[Luke Tierney]

On Fri, 2 Feb 2007, Prof Brian Ripley wrote:

> On Fri, 2 Feb 2007, Vaidotas Zemlys wrote:
>
>> Hi,
>>
>> On 2/2/07, Prof Brian Ripley <ripley at stats.ox.ac.uk> wrote:
>>
>>>> I found the culprit. I was parsing formulas in my code, and I saved
>>>> them in that large object. So the environment came with saved
>>>> formulas. Is there a nice way to say R: "please do not save the
>>>> environments with the formulas, I do not need them?"
>>>
>>> No, but why create them that way?  You could do
>>>
>>> mmodel <- as.formula(mmodel, env=.GlobalEnv)
>>>
>> Hm, but say I have some large object in .GlobalEnv, and I generate
>> mmodel  10 different times and save the result as a list with length
>> 10. Now if I try to save this list, R will save 10 different copies of
>> .GlobalEnv together with aforementioned large object?
>
> No, it saves the environment (here .GlobalEnv), not objects, and there can
> be many shared references.

Just to amplify this point: Only a marker representing .GlobalEnv is
saved; on load into a new session that marker becomes the .GlobalEnv
of the new session.

Best,

luke


>
>>> The R way is to create what you want, not fix up afterwards.
>>>
>>> (I find your code unreadable--spaces help a great deal, so am not sure if
>>> I have understood it correctly.)
>>>
>> Hm, I copied this code directly from Emacs+ESS, maybe the mailer
>> mangled something. What I want to do with this piece of code (I will
>> repaste it here)
>>
>> testf<- function(formula) {
>>   mainform <- formula
>>   if(deparse(mainform[[3]][[1]])!="|") stop("invalid conditioning")
>>   mmodel <- substitute(y~x,list(y=mainform[[2]],x=mainform[[3]][[2]]))
>>   mmodel <- as.formula(mmodel)
>>   list(formula=list(main=mmodel))
>> }
>
> You use no spaces around your operators or after commas.  R does when
> deparsing:
>
>> testf
> function (formula)
> {
>     mainform <- formula
>     if (deparse(mainform[[3]][[1]]) != "|")
>         stop("invalid conditioning")
>     mmodel <- substitute(y ~ x, list(y = mainform[[2]], x = mainform[[3]][[2]]))
>     mmodel <- as.formula(mmodel)
>     list(formula = list(main = mmodel))
> }
>
> because it is (at least to old hands) much easier to read.
>
> IcanreadEnglishtextwithoutanyspacesbutIchoosenotto.Similarly,Rcode.Occasional
> spacesare evenharderto parse.
>
>> is to read formula with condition:
>>
>> formula(y~x|z)
>>
>> and construct formula
>>
>> formula(y~x)
>>
>> I looked for examples in code of coplot in library graphics and
>> latticeParseFormula in library lattice.
>>
>> Vaidotas Zemlys
>> --
>> Doctorate student, http://www.mif.vu.lt/katedros/eka/katedra/zemlys.php
>> Vilnius University
>>
>
>

-- 
Luke Tierney
Chair, Statistics and Actuarial Science
Ralph E. Wareham Professor of Mathematical Sciences
University of Iowa                  Phone:             319-335-3386
Department of Statistics and        Fax:               319-335-3017
    Actuarial Science
241 Schaeffer Hall                  email:      luke at stat.uiowa.edu
Iowa City, IA 52242                 WWW:  http://www.stat.uiowa.edu