[R] Adding meta-data when creating objects. e.g: changing "<-" so to (for example) add "creation time" - how-to and pros/cons?

[Michael Bedward]

Hi Ivan,

It doesn't work because there is no object called "x" in the
function's local scope.

Try this...

function(x, ...) {
 xname <- deparse(substitute(x))
 assign(xname, ...)
 x <- get(xname)
 attr(x, "creation.time") <- Sys.time()
 assign(xname, x, pos=.GlobalEnv)
}

Michael


On 11 November 2010 22:17, Ivan Calandra <ivan.calandra at uni-hamburg.de> wrote:
> Hi,
>
> I have tried this (just to practice):
> assign2 <- function(x, ...){
>  assign(x, ..., envir=.GlobalEnv)
>  attr(get(x, envir=.GlobalEnv), "creation.time") <- Sys.time()
> }
>
> assign2("y", 1:4)
> Error in attr(get(x), "creation.time") <- Sys.time() :
>  could not find function "get<-"
>
> Why doesn't it work?
> If I remove the attr() part,
> identical(y, get("y")) returns TRUE, so why attr() cannot work with it?
>
> Thanks in advance for the clarification,
>
> Ivan
>
>
> Le 11/11/2010 11:16, Michael Bedward a écrit :
>>
>> Hi Tal,
>>
>> Here's a way of doing the first bit...
>>
>> assign2<- function(x, ...) {
>>   xname<- deparse(substitute(x))
>>   assign(xname, ...)
>>   x<- get(xname)
>>   attr(x, "creation.time")<- Sys.time()
>>   assign(xname, x, pos=.GlobalEnv)
>> }
>>
>> Michael
>>
>>
>> On 11 November 2010 20:37, Tal Galili<tal.galili at gmail.com>  wrote:
>>>
>>> My objective is to start having meta-data on objects that I create.
>>> For example, consider the following function:
>>>
>>> assign2<- function(x, ...)
>>> {
>>>  assign("x", ...)
>>> attr(x, "creation time")<- Sys.time()
>>>  x<<- x
>>> }
>>>
>>> assign2("x", 1:4)
>>>
>>> "assign2" assigns to x the vector 1:4, and it then also adds the creation
>>> time of the object.
>>>
>>> (Hat tip goes to Peter Alspach for pointing me to the concept of adding
>>> meta
>>> data to an object using attr)
>>>
>>>
>>> But this function has several major limitations:
>>> 1) It will not work for any assignment other then "x".  For example
>>> assign2("y", 1:4)
>>> Doesn't work.
>>> How might this be fixed ?
>>> 2) This function will probably need to also search the parent environment
>>> if
>>> the variable already exists.  If it does, then there should be a "update
>>> date" instead of "creation date".  But for that to work, I'll need a
>>> solution for problem 1.
>>> 3) How will this handle a case when we are updating only a subset of the
>>> items?  (for example:  assign2("x[1:2]", 8:9) )
>>> 4) My real intention is to somehow change the "<-" operator (not simply
>>> the
>>> assign).  I am unsure as to how to do that.
>>> 5) Are there any major pros/cons to the adding of such meta-data to
>>> objects?
>>> (for example, excessive overhead on memory/performance)
>>> 6) Is there already some system that knows how to do this in R (which I
>>> am
>>> simply ignorant about)?
>>>
>>> Thanks for following through, and for any suggestions/thoughts you might
>>> have.
>>>
>>> Best,
>>> Tal
>>>
>>>
>>>
>>>
>>>
>>> ----------------Contact
>>> Details:-------------------------------------------------------
>>> Contact me: Tal.Galili at gmail.com |  972-52-7275845
>>> Read me: www.talgalili.com (Hebrew) | www.biostatistics.co.il (Hebrew) |
>>> www.r-statistics.com (English)
>>>
>>> ----------------------------------------------------------------------------------------------
>>>
>>>        [[alternative HTML version deleted]]
>>>
>>> ______________________________________________
>>> R-help at r-project.org mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>> PLEASE do read the posting guide
>>> http://www.R-project.org/posting-guide.html
>>> and provide commented, minimal, self-contained, reproducible code.
>>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>
> --
> Ivan CALANDRA
> PhD Student
> University of Hamburg
> Biozentrum Grindel und Zoologisches Museum
> Abt. Säugetiere
> Martin-Luther-King-Platz 3
> D-20146 Hamburg, GERMANY
> +49(0)40 42838 6231
> ivan.calandra at uni-hamburg.de
>
> **********
> http://www.for771.uni-bonn.de
> http://webapp5.rrz.uni-hamburg.de/mammals/eng/mitarbeiter.php
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>