title: Error in `row.names<-.data.frame using mlogit in R language
body: <p>Here are the steps I'm following to do a Multinomial Linear Regression.</p>
  
  <pre><code>&gt; z&lt;-read.table("2008 Racedata.txt", header=TRUE, sep="\t", row.names=NULL)
  
  &gt; head(z)
  
       datekey raceno horseno place winner draw winodds log_odds jwt  hwt
  1 2008091501      1       8     1      1    2    12.0 2.484907 128 1170
  2 2008091501      1      11     2      0    3     8.6 2.151762 123 1135
  3 2008091501      1       6     3      0    5     7.0 1.945910 127 1114
  4 2008091501      1      12     4      0   10    23.0 3.135494 123 1018
  5 2008091501      1      14     5      0    4    11.0 2.397895 113 1027
  6 2008091501      1       5     6      0   14    50.0 3.912023 131  972
  
  &gt; x&lt;-mlogit.data(z,choice="winner",shape="long",id.var="datekey",alt.var="horseno")
  
  Error in `row.names&lt;-.data.frame`(`*tmp*`, value = c("1.8", "1.11", "1.6",  : 
    duplicate 'row.names' are not allowed
  
  In addition: Warning message:
  non-unique values when setting 'row.names': ‚Äò10.2‚Äô, ‚Äò10.4‚Äô, ‚Äò10.8‚Äô,
  ‚Äò100.7‚Äô, ‚Äò101.12‚Äô, ‚Äò102.1‚Äô, ‚Äò102.3‚Äô, ‚Äò103.2‚Äô, ‚Äò103.4‚Äô, 
  ‚Äò103.6‚Äô, ‚Äò104.12‚Äô, ‚Äò104.3‚Äô, ‚Äò104.9‚Äô, ‚Äò105.1‚Äô, ‚Äò105.5‚Äô, 
  ‚Äò105.6‚Äô, ‚Äò105.8‚Äô, ‚Äò106.11‚Äô, ‚Äò106.12‚Äô, ‚Äò106.13‚Äô, ‚Äò106.7‚Äô, 
  ‚Äò107.10‚Äô, ‚Äò107.14‚Äô, ‚Äò107.3‚Äô, ‚Äò108.12‚Äô, ‚Äò108.2‚Äô, ‚Äò108.6‚Äô, 
  ‚Äò108.9‚Äô, ‚Äò109.1‚Äô, ‚Äò109.14‚Äô, ‚Äò109.7‚Äô, ‚Äò11.12‚Äô, ‚Äò11.5‚Äô, 
  ‚Äò11.9‚Äô, ‚Äò110.2‚Äô, ‚Äò110.3‚Äô, ‚Äò110.4‚Äô, ‚Äò110.9‚Äô, ‚Äò111.1‚Äô, 
  ‚Äò111.7‚Äô, ‚Äò112.12‚Äô, ‚Äò112.3‚Äô, ‚Äò112.6‚Äô, ‚Äò112.8‚Äô, ‚Äò113.10‚Äô, 
  ‚Äò113.13‚Äô, ‚Äò113.7‚Äô, ‚Äò114.12‚Äô, ‚Äò114.2‚Äô, ‚Äò114.9‚Äô, ‚Äò115.10‚Äô, 
  ‚Äò115.13‚Äô, ‚Äò115.5‚Äô, ‚Äò116.11‚Äô, ‚Äò116.6‚Äô, ‚Äò117.14‚Äô, ‚Äò117.3‚Äô, 
  ‚Äò117.7‚Äô, ‚Äò118.1‚Äô, ‚Äò118.13‚Äô, ‚Äò118.2‚Äô, ‚Äò118.9‚Äô, ‚Äò119.10‚Äô, 
  ‚Äò119.5‚Äô, ‚Äò119.6‚Äô, ‚Äò119.8‚Äô, ‚Äò12.1‚Äô, ‚Äò12.10‚Äô, ‚Äò12.3‚Äô, 
  ‚Äò12.6‚Äô, ‚Äò120.2‚Äô, ‚Äò120.4‚Äô, ‚Äò120.7‚ [... truncated] 
  &gt; 
  </code></pre>
  
  <p>What step am I missing here? Why the duplicates in row.names?</p>
  
  <p>Thanks,
  Walt</p>