On 4/11/21 11:46 AM, Viechtbauer, Wolfgang (SP) wrote:
The is.vector() thing has also bitten me in the behind on a few occasions. When
I want to check if something is a vector, allow for it to possibly have some
additional attributes (besides names) that would make is.vector() evaluate to
FALSE, but evaluate to FALSE for lists (since is.vector(list(a=1, b=2)) is TRUE
-- which also wasn't what I had initially expected before reading the
documentation), I use:
.is.vector <- function(x)
is.atomic(x) && !is.matrix(x) && !is.null(x)
This might also work:
.is.vector <- function(x)
is(x, "vector") && !is.list(x)
That will allow expression vectors to return TRUE, but they are not
atomic so they would be excluded by your current version.
--
David.
I am sure there are all kinds of edge (and probably also not so edge) cases
where these also fail to work properly. Kinda curious if there are better
approaches out there.
You might want to exclude expression vectors as well.
Best,
Wolfgang
-----Original Message-----
From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of Therneau, Terry
M., Ph.D. via R-help
Sent: Saturday, 10 April, 2021 16:12
To: R-help
Subject: Re: [R] evil attributes
I wrote: "I confess to being puzzled WHY the R core has decided on this
definition..."
After just a little more thought let me answer my own question.
a. The as.vector() function is designed to strip off everything extraneous and
leave just
the core. (I have a mental image of Jack Webb saying "Just the facts
ma'am"). I myself
use it freqently in the test suite for survival, in cases where I'm checking the
corrent
numeric result and don't care about any attached names.
b. is.vector(x) essentially answers the question "does x look like a result of
as.vector?"
Nevertheless I understand Roger's confusion.
--
Terry M Therneau, PhD
Department of Quantitative Health Sciences
Mayo Clinic
thern...@mayo.edu
"TERR-ree THUR-noh"
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