[R] Is it a bug in list() behavior?

[Tony Plate]

As wolski/Eryk's example shows, it seems that "[[" for lists accepts abbreviations, whereas "[" does not.  Is this intended?  (This is a difference from S-plus - both "[" and "[[" for lists accept abbreviations in S-plus (V6.1 for Windows at least.)

I couldn't find any mention of this difference in regards to accepting abbreviations in either ?"[" or section 6.1 of the Introduction to R, or in the R Language Manual, or in the R Reference Manual.  [As an aside, I'd rather that the subset operators didn't accept abbreviations at all,but ...]

The name returned by "[" for a non-existent element of a list also seems of dubious correctness.

> list(abc=123)[["a"]]
[1] 123
> list(abc=123)["a"]
$"NA"
NULL

> list(abc=123)$a
[1] 123
> version
         _              
platform i386-pc-mingw32
arch     i386           
os       mingw32        
system   i386, mingw32  
status                  
major    1              
minor    6.2            
year     2003           
month    01             
day      10             
language R              
>


At Monday 04:54 PM 3/24/2003 +0100, you wrote:
>wolski wrote:
>>Hello!
>>let:
>>test<-1:3
>>list(test)
>>names(test)<-c("X11","X12","Y23")
>>
>>>test[["Y2"]]
>>3
>>I had assumed that the names in a list are like a keys in a hash.
>>Therefore i thought that no value should be returned.
>>The behavior of:
>>
>>>test["Y2"]
>><NA>   NA 
>>is as i expected.
>>
>>Should it be as it is? How is the definition of [[]] and []?
>
>No! See "An Introduction to R", Section 6.1:
>"The names of components may be abbreviated down to the minimum number of letters needed to identify them uniquely. Thus Lst$coefficients may be minimally specified as Lst$coe and Lst$covariance as Lst$cov."
>
>Uwe Ligges
>
>______________________________________________
>R-help at stat.math.ethz.ch mailing list
>https://www.stat.math.ethz.ch/mailman/listinfo/r-help