From: maechler@stat.math.ethz.ch [mailto:maechler@stat.math.ethz.ch]
"possolo" == possolo <possolo@crd.ge.com> writes:
possolo> Full_Name: Antonio Possolo Version: 1.3.1 OS: Linux
possolo> (RH 7.1), Windows 2000 Submission from: (NULL)
possolo> A FEATURE THAT EASILY GENERATES BUGS
possolo> sample(pi, size=1) produces 1, 2, or 3.
possolo> sample(c(pi, pi), size=1) produces 3.141593 always.
possolo> Although this conforms with the behavior explained
possolo> in the help page for "sample", the behavior for the
possolo> case where x (in sample(x, ...)) has length 1 can
possolo> easily lead to errors if x is generated
possolo> automatically and one neglects to check its length
possolo> before sampling from it.
I completely share your opinion; and we (not I) only recently
had a case where a user-written function did not work in some
cases when sample(iv, ...) was used, with an integer
vector iv which sometimes (rarely) was of length one.
In your case with `pi' (which is not an integer), we could make
sample() give a warning at least instead of silently coercing to
integer; in our case however, iv[] *is* an integer vector, just
sometimes of length 1 which is inherently ``non-decidable''.
The reason sample() works as it does is S - compatibility
and that *is* important.
possolo> I believe it would be safest to require x to be
possolo> always the full set of values one wishes to sample
possolo> from, and remove the special meaning that is
possolo> attached to the case when x is of length 1.
What we *could* consider instead, without breaking
back-compatibility,
is adding an additional argument `isVector', e.g.
sample (x, size, replace = FALSE, prob = NULL, isVector = FALSE)
such that if you use
sample(pi, size = 1, isV = TRUE)
you would always get 3.14159..
This would add least make the user written code much nicer to
read than (what is currently needed)
i.rand <- if(length(iv) == 1) iv else sample(iv, .....)
Other opinions? {from Insightful as well -- this would be worth
doing in all implementations of S}