Hi,
On 03/26/2014 10:24 AM, Radford Neal wrote:
From: Richard Cotton <richiero...@gmail.com>
The rep function is very versatile, but that versatility comes at a
cost: it takes a bit of effort to learn (and remember) its syntax.
This is a problem, since rep is one of the first functions many
beginners will come across. Of the three main uses of rep, two have
simpler alternatives.
rep(x, times = ) has rep.int
rep(x, length.out = ) has rep_len
I think that a rep_each function would be a worthy addition for the
third use case
rep(x, each = )
(It might also be worth having rep_times as a synonym for rep.int.)
I think this is exactly the wrong approach. Indeed, the aim should be
to get rid of functions like rep.int (or at least discourage their
use, even if they have to be kept for compatibility).
Why is rep_each(x,n) better than rep(x,each=n)?
According to the NEWS file, it seems that R core felt that having
rep_len() was a good idea.
There is a new function rep_len() analogous to rep.int() for when
speed is required (and names are not).
Now one might wonder (and your students might wonder too) why having
rep_each() "for when speed is required (and names are not)" is not a
good idea.
By having rep_len(), rep_each(), and rep_times(), the 3 extra arguments
in rep(x, ...) would be covered. Plus, when I use tab completion after
typing rep_, I would get a nice summary and would be able to quickly
choose. Right now, when I do this, one function is missing, and one has
a misleading name. So I'd rather have no specialized function at all,
or have the 3. Would be cleaner and less confusing than the current
situation.
Cheers,
H.
There is no saving in
typing (which would be trivial anyway). There *ought* to be no
significant difference in speed (though that seems to have been the
motive for rep.int). Are you trying to let students learn R without
ever learning about specifying arguments by name?
And where would you stop? How about seq_by(a,b,s) rather than having
to arduously type seq(a,b,by=s)? Maybe we should have glm_binomial,
glm_poisson, etc. so we don't have to remember the "family" argument?
This way lies madness...
Radford Neal
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