On 9/2/2009 2:39 PM, Stavros Macrakis wrote:
The documentation for is.atomic and is.recursive is inconsistent with
their behavior in R 2.9.1 Windows.
? is.atomic
'is.atomic' returns 'TRUE' if 'x' is an atomic vector (or 'NULL')
and 'FALSE' otherwise.
...
'is.atomic' is true for the atomic vector types ('"logical"',
'"integer"', '"numeric"', '"complex"', '"character"' and '"raw"')
and 'NULL'.
This description implies that is.atomic(x) implies is.vector(x)
(assuming that an "atomic vector type" is a subset of a "vector
type"). But in fact that is not true for values with class
attributes:
I don't see is.vector mentioned there. The description of is.vector on
its own man page implies the behaviour below; I think the description of
is.atomic that you quote above is also consistent with the behaviour.
One could argue that in R's pre-history we should have had is.atomic
imply is.vector, but that's not how things are documented, and I think
we're pretty much stuck with the definitions we've got on low level
functions like those.
is.atomic(factor(3)) => TRUE
is.vector(factor(3)) => FALSE
is.atomic(table(3)) => TRUE
is.vector(factor(3)) => FALSE
It appears, then, that is.atomic requires only that unclass(x) be an
atomic vector, not that x be an atomic vector.
There is also another case where is.atomic(x) != is.vector(unclass(x)):
is.atomic(NULL) => TRUE
is.vector(NULL) => FALSE
It would be useful to make the documentation consistent with the
implementation. (Presumably by updating the documentation, not
changing the behavior.)
The documentation continues:
'is.recursive' returns 'TRUE' if 'x' has a recursive (list-like)
structure and 'FALSE' otherwise.
...
Most types of language objects are regarded as recursive: those
which are not are the atomic vector types, 'NULL' and symbols (as
given by 'as.name').
But is.recursive(as.name('foo')) == is.recursive(quote(foo)) == FALSE.
That's what it says should happen. symbols such as as.name('foo') are
not recursive.
Duncan Murdoch
Again, it would be useful to make the documentation consistent with
the implementation.
To summarize all this in a table of the most common datatypes:
outerl <-
function(f, a, b)
structure(outer(a,b,Vectorize(f)),
dimnames=list(a,b))
outerl(function(x,f)(match.fun(f))(x),
list(3,factor(c("a","b")),NULL,function()3,as.name("foo"),environment()),
list("class","mode","storage.mode","is.vector","is.atomic","is.recursive"))
class mode storage.mode is.vector
is.atomic is.recursive
3 "numeric" "numeric" "double" "TRUE"
"TRUE" "FALSE" <<< OK
1:2 "factor" "numeric" "integer" "FALSE"
"TRUE" "FALSE" <<< inconsistent
NULL "NULL" "NULL" "NULL" "FALSE"
"TRUE" "FALSE" <<< inconsistent
function () "function" "function" "function" "FALSE"
"FALSE" "TRUE" <<< OK
foo "name" "name" "symbol" "FALSE"
"FALSE" "FALSE" <<< inconsistent
<environment> "environment" "environment" "environment" "FALSE"
"FALSE" "TRUE" <<< OK
Thanks,
-s
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