[R] a question of alphabetical order

Tue Apr 15 17:28:28 CEST 2008

This is a known Mac OS X bug, nothing to do with R which uses the system 
functions (strcoll/wcscoll) for such things.

If you look at the help for sort, it refers you to ?Comparison.  Which 
says

      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.  Beware of making _any_ assumptions about the
      collation order: e.g. in Estonian 'Z' comes between 'S' and 'T',
      and collation is not necessarily character-by-character - in
      Danish 'aa' sorts as a single letter, after 'z'.  Some platforms
      may not respect the locale and always sort in ASCII.  (String
      comparison is always for the part of the string up to the first
      nul if there are embedded nuls.)

Mac OS X (more specifically, 10.5.2 on i386) is one of those disrespectful 
platforms.

> x <- intToUtf8(c(32:127, 160:255), multiple=T)
> order(x)
   [1]   1   2   3   4   5   6   7   8   9  10  11  12  13  14  15  16  17 
18
  [19]  19  20  21  22  23  24  25  26  27  28  29  30  31  32  33  34  35 
36
  [37]  37  38  39  40  41  42  43  44  45  46  47  48  49  50  51  52  53 
54
  [55]  55  56  57  58  59  60  61  62  63  64  65  66  67  68  69  70  71 
72
  [73]  73  74  75  76  77  78  79  80  81  82  83  84  85  86  87  88  89 
90
  [91]  91  92  93  94  95  96  97  98  99 100 101 102 103 104 105 106 107 
108
[109] 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 
126
[127] 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 
144
[145] 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 
162
[163] 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 
180
[181] 181 182 183 184 185 186 187 188 189 190 191 192

which is quite different from Linux or Solaris.  This may not come out, 
but paste(sort(x), collapse="") includes

aAªáÁàÀâÂåÅäÄãÃæÆbBcCçÇdDeEéÉèÈêÊëË

on Linux in es_ES.utf8 .

Platforms are a lot worse at sorting in UTF-8 than 8-bit encodings.  Mac 
OS X has es_ES.ISO8859-15, and that does do a reasonable job including 
aáàâåäãæ .

On Tue, 15 Apr 2008, [Ricardo Rodriguez] Your XEN ICT Team wrote:

> Hi all,
>
> In Spanish vowels with accent like á, é, ... doesn't affect to the
> alphabetical order of vector of strings. I mean, a or á don't matter for
> establishing the alphabetical order.
>
> Nevertheless, while working with R order, here is what I get.
>
> Given a file transport.txt
>
> medio#variable
> avión#34
> barco#33
> bicicleta#3
> ángulo#37
> camión#54
> coche#23
> tren#67
>
> > toPlot <-
> read.csv("~/Desktop/Workplace/transport.txt",header=TRUE,sep="#")
> > toPlot[order(toPlot$medio),]
>      medio variable
> 1     avión       34
> 2     barco       33
> 3 bicicleta        3
> 5    camión       54
> 6     coche       23
> 7      tren       67
> 4    ángulo       37
> >
>
> I expect ángulo appears in the first place as n (in ángulo) goes before
> v (in avión) and á/a doesn't matter for alphabetical order.
>
> But ángulo appears in the last position.
>
> Here my environment:
>
> > sessionInfo()
> R version 2.7.0 beta (2008-04-12 r45280)
> i386-apple-darwin9.2.2
>
> locale:
> es_ES.UTF-8/es_ES.UTF-8/C/C/es_ES.UTF-8/es_ES.UTF-8
>
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  methods   base
> > version
>               _
> platform       i386-apple-darwin9.2.2
> arch           i386
> os             darwin9.2.2
> system         i386, darwin9.2.2
> status         beta
> major          2
> minor          7.0
> year           2008
> month          04
> day            12
> svn rev        45280
> language       R
> version.string R version 2.7.0 beta (2008-04-12 r45280)
> >
>
> Is it not possible to get this dataframe ordered correctly in Spanish?
> Other programs (Excel, for instance) do order correctly.
>
> Thanks for your help,
>
> Ricardo
>
> --
> Ricardo Rodríguez
> Your XEN ICT Team
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

-- 
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