[datatable-help] data.table segfaulting, need help verifying the reason

[Chris Neff]

Oh okay, sorry. Either way it is more than just a slight improvement :)
 But yes that would fix everything.


On Wed, Sep 11, 2013 at 5:33 AM, Arunkumar Srinivasan <aragorn168b at gmail.com
> wrote:

>  Chris,
> It's not filed as a FR, IIRC. It's filed under "Internals".
>
> Arun
>
> On Wednesday, September 11, 2013 at 11:31 AM, Chris Neff wrote:
>
> Yes, dropping names altogether in data.table would fix this, and would be
> the cleanest thing overall since as is said in that thread data.table
> doesn't really work with rownames in mind anyway.
>
> Except it is less of a FR now and more of a bad bug because you can get
> segfaults from it.
>
>
> On Wed, Sep 11, 2013 at 5:24 AM, Arunkumar Srinivasan <
> aragorn168b at gmail.com> wrote:
>
>  Most likely, this<https://r-forge.r-project.org/tracker/index.php?func=detail&aid=4882&group_id=240&atid=5335>,
> when fixed, will take care of it?
>
> Arun
>
> On Wednesday, September 11, 2013 at 11:17 AM, Chris Neff wrote:
>
> Indeed, it shows that k1 and k2 both have names of length 2, and both
> times the value of names is just the variable names.
>
> Where the names are getting added is by apply.  What the issue with
> data.table is that it does not ignore names from short variables. I now
> have a small reproducible example I can share:
>
> d <- data.frame(x=1:5)
>
> f <- function(x) {data.table(x=x, y=1:10)}
>
> l <- apply(d, 1, f)
>
> lapply(l, function(x) lapply(x, names)) # All values of x have a name
>
> a <- rbindlist(l) # a$x will segfault after this
>
>
> The underlying issue is what data.table and data.frame do with rownames
> and recycling. Look at this simple case:
>
> x <- 1:5
> names(x) <- letters[1:5]
>
> df <- data.frame(x=x, y=1:10)
> #Warning message:
> #  In data.frame(x = x, y = 1:10) :
> #  row names were found from a short variable and have been discarded
>
> lapply(df, names) # no names
>
> dt <- data.table(x=x, y=1:1) # No warning
>
> lapply(dt, names) # x has names, and they get recycled.
>
>
> So data.table needs to follow data.frame logic for discarding row names
> when they would otherwise be recycled.
>
>
> Bug submitted here:
> https://r-forge.r-project.org/tracker/index.php?func=detail&aid=4890&group_id=240&atid=975
> I'm surprised this has never arisen before, it seems like something that
> has been around forever.
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