[R] Unexpected result of names<-

[Liaw, Andy]

That's because S does partial matching of component names, if it can be done
unambiguously:


> z <- list(aaa=1, bbb=2)
> z$a
[1] 1
> z[["a"]]
[1] 1
> z["a"]
$"NA"
NULL

> z["aaa"]
$aaa
[1] 1

Andy



From: Hong Ooi
> 
> Hi,
> 
> I came across some rather unexpected behaviour the other day with
> assigning names and lists. Here's an example.
> 
> > z <- list(aaa=1, bbb=2)
> > z
> $aaa
> [1] 1
> 
> $bbb
> [1] 2
> 
> Note that z has members named "aaa" and "bbb". Now:
> 
> > names(z$a) <- "X"
> > z
> $aaa
> [1] 1
> 
> $bbb
> [1] 2
> 
> $a
> X 
> 1
> 
> I would have expected that trying to name z$a would either 
> give an error
> (because z doesn't have an element "a") or would cause z$aaa to be
> modified (due to partial name matching).  I didn't expect that a new
> list member would be created.
> 
> I've checked that this is consistent across SPlus 2000, SPlus 7, and R
> 2.2 for Windows. Can someone give an explanation for why this is
> happening?
> 
> 
> -- 
> Hong Ooi
> Senior Research Analyst, IAG Limited
> 388 George St, Sydney NSW 2000
> (02) 9292 1566
> 
> 
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