[datatable-help] rbindlist

[G See]

I agree.  Here is a related thread:
http://thread.gmane.org/gmane.comp.lang.r.datatable/2231

Garrett


On Tue, Dec 3, 2013 at 8:26 AM, Alexandre Sieira
<alexandre.sieira at gmail.com> wrote:
> I have come across some behavior in rbindlist that look unexpected to me:
>
>> rbindlist(list(data.table(a=1, b=2), data.table(b=4, a=3)))
>    a b
> 1: 1 2
> 2: 4 3
>
> So it appears to assume (without checking) that all objects have not only
> the same column names but also the same column order.  So a value assigned
> to column ‘a’ in the second object was used for column ‘b’ in the end result
> (and vice-versa).
>
> I know the documentation says rbindlist uses the column types from the first
> entry of the list, but I didn’t see any mention to column order or names
> anywhere.
>
> I suggest that column names are matched, even if they are not in the same
> order. Perhaps a ‘use.names’ parameter could be used to ask for this
> behavior to avoid breaking backwards compatibility.
>
> Or, at the very least, I suggest the documentation of bindlist be updated to
> explicitly mention that the columns will be considered by position only, and
> that callers need to ensure the column orders of all objects match exactly.
> And that a warning is issued by rbindlist when the column names don’t match.
>
> --
> Alexandre Sieira
> CISA, CISSP, ISO 27001 Lead Auditor
>
> "The truth is rarely pure and never simple."
> Oscar Wilde, The Importance of Being Earnest, 1895, Act I
>
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