[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 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
>
>
>
>
>
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