R help - Mar 2003 - Is it a bug in list() behavior?

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 []?

/Eryk

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

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
>
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