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

unlist(l[1:5])

sum(l[1:5])

Herv?:

Kindly explain this, then:

l <- as.list(1:10)
is.atomic(l) # FALSE

[1] FALSE

index <- c(rep(1,5),rep(2,5))


tapply(l,index,unlist)

$`1`
[1] 1 2 3 4 5

$`2`
[1]  6  7  8  9 10

## But

tapply(l,index, sum)

Error in FUN(X[[i]], ...) : invalid 'type' (list) of argument

Cheers,
Bert
Bert Gunter

"The trouble with having an open mind is that people keep coming along
and sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Tue, Feb 14, 2017 at 5:10 PM, Herv? Pag?s <hpages at fredhutch.org> wrote:

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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Herv? Pag?s

Program in Computational Biology
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