>>>>> "Robin" == Robin Hankin <[EMAIL PROTECTED]>
>>>>> on Fri, 27 Jul 2007 08:33:18 +0100 writes:
Robin> On 27 Jul 2007, at 08:07, [EMAIL PROTECTED]
Robin> wrote:
>> This is as doumented, and I think you could say the same
>> thing of seq(). BTW, sequence() allows negative inputs,
>> and I don't think you want sum(input) in that case.
>>
>> I've never seen the point of sequence(), but it has been
>> around in R for a long time. It is used in packages eRm,
>> extRemes, hydrosanity, klaR, seas. Who knows what people
>> have in private code, so I don't see any compelling case
>> to change it. If people want a different version, it
>> would only take a minute to write (see below).
>>
>> We could make seq_len take a vector argument, but as you
>> point out in a followup that makes it slower in the
>> common case. It also changes its meaning if a length > 1
>> vector is supplied, and would speed matter in the
>> long-vector case? What does
>>
>> sequence0 <- function (nvec) { s <- integer(0) for (i in
>> nvec) s <- c(s, seq_len(i)) s }
>>
>> not do that is more than a very rare need?
>>
Robin> My 2 cents:
Robin> Defining
Robin> mySequence <-
Robin> function(x){unlist(sapply(x,function(i){seq_len(i)}))}
Robin> is much faster.
Robin> Neither sequence0() nor mySequence() accepts vectors
Robin> with any element <0 although as Brian Ripley points
Robin> out, sequence() itself does (which I think is
Robin> undesirable).
Yes, I agree.
Some more historical perspective (Brian alluded to) :
As the third R core member (first after Robert & Ross),
I still have access to the following R version
{on one very old fortunately still running Solaris machine; I'm
pretty sure it would not compile anymore on any recent
OS/compiler suite} :
--------------------------------------------------------------------------
..$ R-0.00alpha
R Alpha-Test Version, Copyright (C) 1995 Robert Gentleman and Ross Ihaka
R is free software and comes with ABSOLUTELY NO WARRANTY.
You are welcome to redistribute it under certain conditions.
Type `license()' for details.
> sequence
function (nvec)
{
sequence <- NULL
for (i in (1:length(nvec))) sequence <- c(sequence, seq(nvec[i]))
sequence
}
>
--------------------------------------------------------------------------
which interestingly also "works" for negative nvec[i],
but the way it is written even more clearly suggests that
negative nvec entries were not the intent.
I'm voting that R should adopt a new (fast, but R code
only) version of sequence() which gives an error for negative
'nvec' entries --- though I do agree with Brian that it's not
really an important function at all.
Martin Maechler, ETH Zurich
PS:
Note that this was before R became GPL'ed "Free software", and
that the R version stems from the following place -- back in 1995 :
/[EMAIL PROTECTED]:/pub/R/unix/
-rw-r--r-- 1 51 1371 Jun 20 1995 INSTALL
-rw-r--r-- 1 51 466232 Jun 20 1995 R-unix-src.tar.gz
-rw-r--r-- 1 51 1079 Jun 20 1995 README
______________________________________________
R-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel
