[R] reverse lexicographic order

[Prof Brian Ripley]

On 14 Dec 2003, Peter Dalgaard wrote:

> Thomas W Blackwell <tblackw at umich.edu> writes:
> 
> > Murray  -
> > 
> > If you could guarantee that all of the email addresses have
> > exactly one occurrence of the "@" character in them, then
> > something like
> ....snip....
> 
> Otherwise, try something like this (I don't think we have a string
> reversal function anywhere, do we?):

Only in the examples for strsplit ....

> 
> > mychar <- scan(what="")
> 1: I have some email addresses that I would like to sort in reverse
> 14: lexicographic order so that addresses from the same domain will be
> 25: grouped together. How might that be done?
> 32:
> Read 31 items
> >
> >mychar[order(sapply(lapply(strsplit(mychar,""),rev),paste,collapse=""))]
>  [1] "together."     "done?"         "I"             "I"
>  [5] "lexicographic" "grouped"       "would"         "be"
>  [9] "be"            "the"           "like"          "same"
> [13] "some"          "reverse"       "have"          "email"
> [17] "will"          "from"          "in"            "domain"
> [21] "so"            "to"            "order"         "addresses"
> [25] "addresses"     "that"          "that"          "that"
> [29] "might"         "sort"          "How"
> 
> 
> 
> > > Hi all,
> > >
> > > I have some email addresses that I would like to sort in reverse
> > > lexicographic order so that addresses from the same domain will be
> > > grouped together. How might that be done?
> > >
> > > Murray
> > >
> > > --
> > > Dr Murray Jorgensen      http://www.stats.waikato.ac.nz/Staff/maj.html
> > > Department of Statistics, University of Waikato, Hamilton, New Zealand
> > > Email: maj at waikato.ac.nz                                Fax 7 838 4155
> > > Phone  +64 7 838 4773 wk    +64 7 849 6486 home    Mobile 021 1395 862
> > >
> > > ______________________________________________
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> > >
> > 
> > ______________________________________________
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> > 
> 
> 

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595