I did look at the Comparison help but totally overlooked this part;
Comparison of strings in character vectors is lexicographic within
the strings using the collating sequence of the locale in use: see
‘locales’. The collating sequence of locales such as ‘en_US’ is
normally different from ‘C’ (which should use ASCII) and can be
surprising.
I've recently changed to a different Linux distribution and was trying
to work out why I was getting a different order of the factor levels
even though it was the same code. I thought I'd inadvertantly changed
something somehow.
Much clearer now -- even if still confusing.
Thanks for the pointer.
On Fri, 18-Mar-2016 at 10:19AM +0100, peter dalgaard wrote:
|> Ooops, that was answering the question you actually asked. The one you meant
to ask is answered by this part:
|>
|> The sort order for character vectors will depend on the collating sequence
of the locale in use: see Comparison.
|>
|> ...and collating sequences is a weird and woolly subject, where you cannot
even be sure that locales of the same name on two different platforms sort
strings in the same order.
|>
|> -pd
|>
|>
|>
|> On 18 Mar 2016, at 10:13 , peter dalgaard <pda...@gmail.com> wrote:
|>
|> >
|> > On 18 Mar 2016, at 10:02 , Patrick Connolly <p_conno...@slingshot.co.nz>
wrote:
|> >
|> >> I don't follow why this happens:
|> >>
|> >>> sort(c(LETTERS[1:5], letters[1:5]))
|> >> [1] "a" "A" "b" "B" "c" "C" "d" "D" "e" "E"
|> >>
|> >> The help for sort() says:
|> >>
|> >> method: character string specifying the algorithm used. Not
|> >> available for partial sorting. Can be abbreviated.
|> >>
|> >> But what are the methods available? The help mentions xtfrm but that
|> >> doesn't illuminate, I'd have thought that at least by default it would
|> >> have something to do with ASCII codes. But that's not the case since
|> >> all the uppercase ones would be before the lowercase ones.
|> >>
|> >> I know something different is happening but I don't know what it is
|> >> (do you, Mr Jones?). Apologies to Bob Dylan.
|> >>
|> >
|> >
|> > Um, read _all_ of the help file?
|> >
|> > sort.int(x, partial = NULL, na.last = NA, decreasing = FALSE,
|> > method = c("shell", "quick"), index.return = FALSE)
|> >
|> > [snip]
|> >
|> > Method "shell" uses Shellsort (an O(n^{4/3}) variant from Sedgewick
(1986)). If x has names a stable modification is used, so ties are not
reordered. (This only matters if names are present.)
|> >
|> > Method "quick" uses Singleton (1969)'s implementation of Hoare's Quicksort
method and is only available when x is numeric (double or integer) and partial
is NULL. (For other types of x Shellsort is used, silently.) It is normally
somewhat faster than Shellsort (perhaps 50% faster on vectors of length a
million and twice as fast at a billion) but has poor performance in the rare
worst case. (Peto's modification using a pseudo-random midpoint is used to make
the worst case rarer.) This is not a stable sort, and ties may be reordered.
|> >
|> > Factors with less than 100,000 levels are sorted by radix sorting when
method is not supplied: see sort.list.
|> >
|> > -pd
|> >
|> >
|> > --
|> > Peter Dalgaard, Professor,
|> > Center for Statistics, Copenhagen Business School
|> > Solbjerg Plads 3, 2000 Frederiksberg, Denmark
|> > Phone: (+45)38153501
|> > Office: A 4.23
|> > Email: pd....@cbs.dk Priv: pda...@gmail.com
|>
|> --
|> Peter Dalgaard, Professor,
|> Center for Statistics, Copenhagen Business School
|> Solbjerg Plads 3, 2000 Frederiksberg, Denmark
|> Phone: (+45)38153501
|> Office: A 4.23
|> Email: pd....@cbs.dk Priv: pda...@gmail.com
|>
--
~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.
___ Patrick Connolly
{~._.~} Great minds discuss ideas
_( Y )_ Average minds discuss events
(:_~*~_:) Small minds discuss people
(_)-(_) ..... Eleanor Roosevelt
~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.
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