[datatable-help] setkey removes attribute settings

[Thell]

On Jun 9, 2:18 am, Matthew Dowle <mdo... at mdowle.plus.com> wrote:
> ... and I added a comment and link back to this thread, to this FR :https://r-forge.r-project.org/tracker/index.php?func=detail&aid=1006&...
> setkey doesn't retain user attributes because it (currently) copies the
> data.table, something we'd like to improve anyway.
> Matthew
>
>
>
> On Wed, 2011-06-08 at 22:34 -0400, Steve Lianoglou wrote:
> > Hi,
>
> > On Wed, Jun 8, 2011 at 7:01 PM, Thell Fowler <tbfowl... at gmail.com> wrote:
>
> > > It looks like custom attributes are lost by a DF to DT creation, and when the key info for a DT is invalidated, altered, etc...  I ran into this when trying to attach some attribute info to a table that identifies column groups so that a new global variable or passing another param to functions wouldn't be needed.  This worked nicely, until I had need to either modify some data in the table, which invalidates the key...
>
> > > Was this a design decision?  If so, why?
>
> > Try `as.data.table` for a more "delicate" way to convert a data.frame
> > to a data.table. Your attributes will come through to the other side.
>
> > R> df <- data.frame( id=c(1:5), name= letters[1:5] )
> > R> attr(df, 'testing') <- 'keep me'
> > R> dt <- as.data.table(df)
> > R> attr(dt, 'testing')
> > [1] "keep me"
>
> > -steve
>
>

Thank you for the quick replies, for adding this detail to the feature
request, and for the as.data.table hint (which I'll be testing today).

I guess for now, in instances when a function will invalidate the keys
and return the table I'll copy out the specific attributes for column
groups, then restore them prior to passing the table back.

Sincerely,
Thell