R help - Jul 2007 - is.null doesn't work

Hi,

What's wrong here?:
> v=c(`-`,`+`,1,`^`,`^`,NA,NA,"X",9,"X",2)
> i2=16
> v[i2]
[[1]]
NULL
> is.null(v[i2])
[1] FALSE

Is it a bug or have I misunderstood something?

Atte Tenkanen
University of Turku, Finland

Seems to work, if I unlist the argument at first ;-)

Atte
> Hi,
> 
> What's wrong here?:
> 
> > v=c(`-`,`+`,1,`^`,`^`,NA,NA,"X",9,"X",2)
> > i2=16
> > v[i2]
> [[1]]
> NULL
> 
> > is.null(v[i2])
> [1] FALSE
> 
> Is it a bug or have I misunderstood something?
> 
> Atte Tenkanen
> University of Turku, Finland
>

'v' appears to be a list:
>  v=c(`-`,`+`,1,`^`,`^`,NA,NA,"X",9,"X",2)
>  i2=16
>  v[i2]
[[1]]
NULL
> str(v)
List of 11
 $ :function (e1, e2)
 $ :function (e1, e2)
 $ : num 1
 $ :function (e1, e2)
 $ :function (e1, e2)
 $ : logi NA
 $ : logi NA
 $ : chr "X"
 $ : num 9
 $ : chr "X"
 $ : num 2

because you used backquotes(`) on the '-'; notice the difference:
> str(c(`-`,1))
List of 2
 $ :function (e1, e2)
 $ : num 1
> str(c('-',1))
 chr [1:2] "-" "1"
>



On 7/12/07, Atte Tenkanen <attenka at utu.fi>
wrote:
> Hi,
>
> What's wrong here?:
>
> > v=c(`-`,`+`,1,`^`,`^`,NA,NA,"X",9,"X",2)
> > i2=16
> > v[i2]
> [[1]]
> NULL
>
> > is.null(v[i2])
> [1] FALSE
>
> Is it a bug or have I misunderstood something?
>
> Atte Tenkanen
> University of Turku, Finland
>
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>

-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem you are trying to solve?