Re: [R] Age of an object?

From: Kjetil Brinchmann Halvorsen <>
Date: Wed 14 Dec 2005 - 23:37:35 EST

Philippe Grosjean wrote:
> Martin Maechler wrote:

>>>>>>> "Trevor" == Trevor Hastie <>
>>>>>>>    on Tue, 13 Dec 2005 12:51:34 -0800 writes:
>>     Trevor> It would be nice to have a date stamp on an object.

One way to do this with important objects is to use the comment function (in package base)

comment(myobj) <- "made last sunday of 2005"


>>     Trevor> In S/Splus this was always available, because objects were files.
>>    [are you sure about "always available"? 
>>     In any case, objects were not single files anymore for a
>>     long time, at least for S+ on windows, and AFAIK also on
>>     unixy versions recently ]
>> This topic has come up before.
>> IIRC, the answer was that for many of us it doesn't make sense
>> most of the time: 

> I remember it was discussed several times. I don't remember why it was
> considered too difficult to do.
>> If you work with *.R files ('scripts') in order to ensure
>> reproducibility, you will rerun -- often source() -- these files,
>> and the age of the script file is really more interesting.
>> Also, I *always* use the equivalent of  q(save = "no") and
>> almost only use save() to particularly save the results of
>> expensive  computations {often, simulations}.

> OK, now let me give examples where having such an information would ease
> the work greatly: you have a (graphical) view of the content of an
> object (for instance, the one using the "view" button in R commander),
> or you have a graphical object explorer that has a cache to speed up
> display of information about objects in a given workspace (for instance,
> the SciViews-R object explorer). What a wonderful feature it will be to
> tell if an object was changed since last query. In the view, one could
> have a visual clue if it is up-to-date or not. In the object explorer, I
> could update information only for objects that have changed...
>>     Trevor> I have looked around, but I presume this information is not available.
>> I assume you will get other answers, more useful to you, which
>> will be based on a class of objects which carry an
>> 'creation-time' attribute.  

> Yes, but that would work only for objects designed that way, and only if
> the methods that manipulate that object do the required housework to
> update the 'last-changed' attribute (the question was about last access
> of an object, not about its creation date, so 'last-changed' is a better
> attribute here). If you access the object directly with, let's say,
> myobject@myslot <- newvalue, that attribute is not updated, isn't it?
> Best,
> Philippe Grosjean
>> Martin Maechler, ETH Zurich
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> mailing list PLEASE do read the posting guide! Received on Wed Dec 14 23:48:03 2005

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