[datatable-help] Error on := causes data.table to be left in a bad state

[Chris Neff]

Whoops thats what I get for trying to recreate examples by memory.

Bug report: https://r-forge.r-project.org/tracker/index.php?func=detail&aid=1711&group_id=240&atid=975

On 16 December 2011 11:10, Matthew Dowle <mdowle at mdowle.plus.com> wrote:
>
> Agreed. That doesn't seem to be precisely what you really had at the
> prompt (notice the 10 vs 100) but a good find, yes, please raise.
>
>> 99% positive this is a bug but I like to get confirmation before
>> making reports.  Still on 2.12.1 64-bit R on Linux, latest SVN version
>> of data.table with debugging turned on.
>>
>> If you do
>>
>> DT <- data.table(x=1:10)
>>
>> DT[, a := letters]
>>
>>
>> You will get the error:
>>
>> Error in `[.data.table`(DT, , `:=`(a, letters)) :
>>   Tried to assign 26 items to target of 100 (can recycle but must be
>> exact multiple). If users ask us to change this to a warning, we will
>> change it; please ask maintainer('data.table').
>>
>>
>> Which is fine.  However, the state of DT after that is that DT has two
>> columns, x (the column it started with) and a, a column full of NULL
>> values. If I then try to do something like
>>
>> DT[, a:=5]
>>
>> It will say the following error:
>>
>> Error in `[.data.table`(DT, , `:=`(a, 5)) :
>>   cannot coerce type 'double' to vector of type 'NULL'
>>
>>
>> Finally, if I make DT bigger, and try the same thing:
>>
>> DT <- data.table(x=1:1e6)
>> DT[, a := letters]
>>
>> It will give me the same error message, but now the state of DT is
>> even more screwed up. If I try to just print DT I get:
>>
>>> DT
>> Error in names(ans) = names(x) :
>>   'names' attribute [2] must be the same length as the vector [1]
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>>
>
>