On 02/14/2017 06:39 PM, Bert Gunter wrote:
Yes, exactly.
So my point is that this:
"X: a vector-like object that supports subsetting with `[`, typically
an atomic vector."
is incorrect, or at least a bit opaque, without further emphasizing
that FUN must accept the result of "[".
Maybe this kind of details belong to the description of the FUN
argument. However please note that the man page for lapply() or the
other *apply() functions don't emphasize the fact that the supplied
FUN must be a function that accepts the things it applies to either,
and nobody seems to make a big deal of it. Maybe because it's obvious?
With atomic vectors, the error
that you produced was obvious, but with lists, I believe not so.
Well, it's the same error. Maybe what's not obvious is that in both
cases the error is coming from sum(), not from tapply() itself.
sum() is complaining that it receives something that it doesn't
know how to handle. The clue is in how the error message starts:
Error in FUN(X[[i]], ...):
Maybe one could argue this is a little bit cryptic. Note the difference
when the error is coming from tapply() itself:
> X <- letters[1:9]
> INDEX <- c(rep(1,5),rep(2,5))
> tapply(X, INDEX, FUN=identity)
Error in tapply(X, INDEX, FUN = identity) :
arguments must have same length
H.
I Appreciate the desire for brevity, but I think clarity should be the
primary goal. Maybe it *is* just me, but I think a few extra words of
explanation here would not go amiss.
But, anyway, thanks for the clarification.
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 6:04 PM, Hervé Pagès <hpa...@fredhutch.org> wrote:
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.4...@gmail.com>
wrote:
Hervé:
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, Hervé Pagès <hpa...@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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--
Hervé Pagès
Program in Computational Biology
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Fred Hutchinson Cancer Research Center
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______________________________________________
R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
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PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
--
Hervé Pagès
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: hpa...@fredhutch.org
Phone: (206) 667-5791
Fax: (206) 667-1319
--
Hervé Pagès
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: hpa...@fredhutch.org
Phone: (206) 667-5791
Fax: (206) 667-1319
______________________________________________
R-help@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.
