Is a list an atomic object? (or is there an issue with the help page of ?tapply ?)
Right. More precisely the function passed thru the FUN argument must work on the subsets of X generated internally by tapply(). You can actually see these subsets by passing the identity function: X <- letters[1:10] INDEX <- c(rep(1,5),rep(2,5)) tapply(X, INDEX, FUN=identity) # $`1` # [1] "a" "b" "c" "d" "e" # # $`2` # [1] "f" "g" "h" "i" "j" Doing this shows you how tapply() splits the vector-like object X into a list of subsets. If you replace the identity function with a function that cannot be applied to these subsets, then you get an error: tapply(X, INDEX, FUN=sum) # Error in FUN(X[[i]], ...) : invalid 'type' (character) of argument As you can see, here we get an error even though X is an atomic vector. H.
On 02/14/2017 05:41 PM, Richard M. Heiberger wrote:
The problem with Bert's second example is that sum doesn't work on a list. The tapply worked correctly.
unlist(l[1:5])
[1] 1 2 3 4 5
sum(l[1:5])
Error in sum(l[1:5]) : invalid 'type' (list) of argument On Tue, Feb 14, 2017 at 8:28 PM, Bert Gunter <bgunter.4567 at gmail.com> wrote:
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 Division of Public Health Sciences Fred Hutchinson Cancer Research Center 1100 Fairview Ave. N, M1-B514 P.O. Box 19024 Seattle, WA 98109-1024 E-mail: hpages at fredhutch.org Phone: (206) 667-5791 Fax: (206) 667-1319
______________________________________________ R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
______________________________________________ R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Herv? Pag?s Program in Computational Biology Division of Public Health Sciences Fred Hutchinson Cancer Research Center 1100 Fairview Ave. N, M1-B514 P.O. Box 19024 Seattle, WA 98109-1024 E-mail: hpages at fredhutch.org Phone: (206) 667-5791 Fax: (206) 667-1319