[R] Is a list an atomic object? (or is there an issue with the help page of ?tapply ?)

[Hervé Pagès]

Hi,

tapply() will work on any object 'X' that has a length and supports
single-bracket subsetting. These objects are sometimes called
"vector-like" objects. Atomic vectors, lists, S4 objects with a "length"
and "[" method, etc... are examples of "vector-like" objects.

So instead of saying

   X: an atomic object, typically a vector.

I think it would be more accurate if the man page was saying something
like

   X: a vector-like object that supports subsetting with `[`, typically
      an atomic vector.

H.

On 02/04/2017 04:17 AM, Tal Galili wrote:
> In the help page of ?tapply it says that the first argument (X) is "an
> atomic object, typically a vector."
>
> However, tapply seems to be able to handle list objects. For example:
>
> ###################
>
> l <- as.list(1:10)
> is.atomic(l) # FALSE
> index <- c(rep(1,5),rep(2,5))
> tapply(l,index,unlist)
>
>> tapply(l,index,unlist)
> $`1`
> [1] 1 2 3 4 5
>
> $`2`
> [1]  6  7  8  9 10
>
>
> ###################
>
> Hence, does it mean a list an atomic object? (which I thought it wasn't) or
> is the help for tapply needs updating?
> (or some third option I'm missing?)
>
> Thanks.
>
>
>
>
>
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-- 
Hervé Pagès

Program in Computational Biology
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