[datatable-help] unique

[Matthew Dowle]

The NA in the key seems to be the issue. duplicated.data.table calls
diff on the columns and assumes no NA in keys.
Can't remember - did we decide to disallow NA in keys? There were other
issues with NA in keys and some threads in the past.
Do you need the key to contain NA?
Matthew


On Sat, 2011-06-25 at 16:23 -0500, Damian Betebenner wrote:
> All,
> 
>  
> 
> I have a simple question regarding the behavior of unique with more
> than 1 key. Consider the example:
> 
>  
> 
> > dt <- data.table(X=c(NA,1,2,3), Y=c(NA,2,1,3))
> 
> > dt
> 
>       X  Y
> 
> [1,] NA NA
> 
> [2,]  1  2
> 
> [3,]  2  1
> 
> [4,]  3  3
> 
> > key(dt) <- c("X", "Y")
> 
> > unique(dt)
> 
>       X  Y
> 
> [1,] NA NA
> 
> [2,]  2  1
> 
> [3,]  3  3
> 
>  
> 
> If I understand this correctly, unique see rows 2 and 3 of dt as the
> same. 
> 
>  
> 
> Is this the behavior one wants?
> 
>  
> 
> Thanks for any clarification.
> 
>  
> 
> Damian
> 
>  
> 
>  
> 
> 
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