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

[Frank Erickson]

There's also a[["x"]], I suppose... :)

and, looking at methods(`[`) ...

`[.listof`(a,1)
`[.data.frame`(a,1)

if it's in the 1st column.

Because we can't fully see your example, maybe you'll want to look at these
other segfault stories:
http://stackoverflow.com/search?q=segfault+%5Bdata.table%5D I think they're
both fixed with the latest R and data.table, though.

--Frank

p.s. Sorry for the double reply, Chris; forgot to use "reply to all"


On Tue, Sep 10, 2013 at 1:59 PM, Frank Erickson <FErickson at psu.edu> wrote:

> There's also a[["x"]], I suppose... :)
>
> and, looking at methods(`[`) ...
>
> `[.listof`(a,1)
> `[.data.frame`(a,1)
>
> if it's in the 1st column.
>
> Because we can't fully see your example, maybe you'll want to look at
> these other segfault stories:
> http://stackoverflow.com/search?q=segfault+%5Bdata.table%5D I think
> they're both fixed with the latest R and data.table, though.
>
> --Frank
>
>
>
> On Tue, Sep 10, 2013 at 1:47 PM, Chris Neff <caneff at gmail.com> wrote:
>
>> Narrowing it down further,
>>
>> a$x
>>
>> segfaults and
>>
>> a[,x]
>>
>> segfaults but
>>
>> a[,"x", with=FALSE]
>>
>> doesn't.
>>
>>
>> On Tue, Sep 10, 2013 at 1:32 PM, Chris Neff <caneff at gmail.com> wrote:
>>
>>> I'm pretty sure it is some issue of a column that thinks it is bigger
>>> than it actually is.  I have tried, so far in vain, to make a reproducible
>>> example that I can share.  I have one, but can't share it.
>>>
>>> What happens is this:
>>>
>>> A data.frame is made:
>>>
>>> > d = data.frame(...)
>>>
>>> Then I call apply over every row, calling a different function that
>>> takes in a DT as well:
>>>
>>> l = apply(d, 1, function(x) func(x[1], x[2], DT))
>>>
>>> This returns a data.frame.  If I rbindlist this:
>>>
>>> a = rbindlist(l)
>>>
>>> I can print a just fine, and it will show me all data like normal. but
>>> if I try to just do
>>>
>>> a$x
>>>
>>> x is one of the columns that was a key in DT, then it segfaults.  If I
>>> ask for a column that was made by "func" and wasn't a column in DT, it
>>> works fine.  If I ask for only the first 10 rows and then ask for x:
>>>
>>> a[1:10]$x
>>>
>>> it works fine.
>>>
>>> So somewhere these key columns think they are different lengths than
>>> they really are, and when I try to access it I go into memory I shouldn't
>>> so I segfault.  How can I verify this? Is there something about the DT I
>>> can check to see what DT thinks these columns are?
>>>
>>>
>>> Also, if instead of apply when making the list, I do
>>>
>>> l = lapply(1:nrow(d), function(i) func(x[i,1],x[i,2],DT))
>>>
>>> and rbindlist that, it works fine too.
>>>
>>>
>>
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>>
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>>
>
>
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