From deepayan.sarkar at gmail.com  Wed May 26 12:33:00 2010
From: deepayan.sarkar at gmail.com (Deepayan Sarkar)
Date: Wed, 26 May 2010 16:03:00 +0530
Subject: [Rd] Indexing bug?
In-Reply-To: <4BFCF092.2010501@gmail.com>
References: <4BFCF092.2010501@gmail.com>
Message-ID: <AANLkTikyON896UMtfDea7aLiWlN97b352e82F19aWkFI@mail.gmail.com>

On Wed, May 26, 2010 at 3:27 PM, Duncan Murdoch
<murdoch.duncan at gmail.com> wrote:
> Is this expected behaviour?
>
> x <- factor(c("c", "b", "a","c"))
> results <- c(c=4, b=5)
> results[x]
>
> giving
>
>> results[x]
> <NA> ? ?b ? ?c <NA>
> ?NA ? ?5 ? ?4 ? NA
>
> (i.e. it appears to give results[levels(x)]

I would say it gives

results[as.numeric(x)]

and it's not clear if that is less "expected". E.g., what happens if
results has no names? results[as.numeric(x)] would still work, but not
results[as.character(x)].

Factors have a dual nature (character labels vs numeric codes), and
when forced to choose, I think it's reasonable to choose the solution
which works more generally.

-Deepayan


>
>
> whereas results[as.character(x)] does what I expected:
>
> as.character(x)
> results[as.character(x)]
>
>> as.character(x)
> [1] "c" "b" "a" "c"
>> results[as.character(x)]
> ?c ? ?b <NA> ? ?c
> ?4 ? ?5 ? NA ? ?4
>
> Duncan Murdoch
>
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>



[Rd] Indexing bug?
Deepayan Sarkar