[Rd] is.vector(as.vector(data.frame(a=1))) and is.vector(as.vector(call("c"))) are FALSE

[Suharto Anggono Suharto Anggono]

These are deviations from the convention: ‘is.vector(as.vector(x, m), m)’ should be true for any mode ‘m’, including the default ‘"any"’.


* Case 1

These are documented.
- ‘is.vector’ returns ‘TRUE’ if ‘x’ is a vector of the specified mode having no attributes _other than names_.  It returns ‘FALSE’ otherwise.
- ‘as.vector’ removes _all_ attributes including names for results of atomic mode (but not those of mode ‘"list"’ nor ‘"expression"’).

Because of the quirk of 'as.vector' for result of mode "list", is.vector(as.vector(data.frame(a=1))) returns FALSE.

> is.vector(as.vector(data.frame(a=1)))
[1] FALSE
> is.vector(as.vector(data.frame(a=1), "list"), "list")
[1] FALSE


* Case 2

as.vector(call("c")) (mode="any", the default) is not an error.
On the other hand, as documented, if ‘mode = "any"’, ‘is.vector’ may return ‘TRUE’ for the atomic modes, ‘list’ and ‘expression’.
As a result, is.vector(as.vector(call("c"))) returns FALSE.

> is.vector(as.vector(call("c")))
[1] FALSE


> sessionInfo()
R version 3.0.1 (2013-05-16)
Platform: i386-w64-mingw32/i386 (32-bit)

locale:
[1] LC_COLLATE=English_United States.1252
[2] LC_CTYPE=English_United States.1252
[3] LC_MONETARY=English_United States.1252
[4] LC_NUMERIC=C
[5] LC_TIME=English_United States.1252

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base