[datatable-help] rbind() vs. rbindlist() behavior/warning

[G See]

I really meant that I thought that do.call(rbind, list(a, b)) would be
slower than rbindlist(list(a, b)).  e.g. when you don't know the
length of the list of data.tables

On Sat, Nov 9, 2013 at 11:44 AM, Arunkumar Srinivasan
<aragorn168b at gmail.com> wrote:
> I am not aware of the status now after eddi's recent edits. "rbindlist"
> initially only checked the type of the first data.table's columns. But now I
> guess with eddi's changes, it does look-down and decide based on class
> hierarchy. That is, if column 1 of dt1 is integer, but of dt2 is numeric,
> it's now "numeric", but before it was "integer". I guess this'll affect the
> speed. I've not done any benchmarking yet. But I'm guessing it'll be slower
> than at least the previous version.
>
> Eddi, any thoughts on this?
>
> Arun
>
> On Saturday, November 9, 2013 at 6:38 PM, G See wrote:
>
> Isn't rbindlist(myList) faster than do.call(rbind, myList)?
>
> Garrett
>
> On Sat, Nov 9, 2013 at 11:33 AM, Arunkumar Srinivasan
> <aragorn168b at gmail.com> wrote:
>
> GSee, I find this a bit confusing at the moment as well - the convergence of
> "rbind" and "rbindlist" and therefore the future of "rbindlist".
>
> `rbindlist` gained speed (to some extent) by assuming things like this and
> skipping checks in the first place. So, should we include checks like this?
> Also, if "rbind" and/or "rbindlist" are made to do the exact same thing,
> then, what's the purpose of "rbindlist"?
>
> Any thoughts?
>
> Arun
>
> On Saturday, November 9, 2013 at 6:29 PM, Eduard Antonyan wrote:
>
> Fyi, it's not well documented, but setting use.names=FALSE in rbind would
> replicate rbindlist behavior.
>
> I think it's a reasonable FR - if/when all of rbind code goes into C, it
> would be trivial to add.
>
> On Nov 9, 2013 10:51 AM, "G See" <gsee000 at gmail.com> wrote:
>
> Hi,
>
> Please note the inconsistency between the behavior of rbind() and
> rbindlist() below.
>
> m1 <- as.data.table(mtcars)
> m2 <- copy(m1)
> rbind(m1[, .SD[1], by=cyl], m2) # Gives warning and binds by name
> rbindlist(list(m1[, .SD[1], by=cyl], m2)) # no warning, and does NOT
> bind by name
>
> What do you think about making them have the same behavior and/or
> warning? Personally, I prefer the behavior of rbind(), and would
> prefer to see a warning if column names are ignored like they are with
> rbindlist().
>
> Thanks,
> Garrett
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