title: R error: Error in `row.names<-.data.frame`(`*tmp*`, value = value)
body: <p>I just make up a data set to test the function "mlogit" which stands for "multinomial logistic regression model"</p>
  
  <p>The data is simply:</p>
  
  <pre><code>head(dat)
     y x1 x2 x3
   1 4  1 18  4
   2 5  1 20  5
   3 2  1 25  3
   4 3  0 26  6
   5 4  0 26  8
   6 3  1 27  4
  </code></pre>
  
  <p>Then when I type</p>
  
  <pre><code>fit &lt;- mlogit(y ~ x1 + x2 + x3, data=dat)
  </code></pre>
  
  <p>the following Message appears:</p>
  
  <pre><code>Error in `row.names&lt;-.data.frame`(`*tmp*`, value = value) : 
    invalid 'row.names' length
  </code></pre>
  
  <p>Does anyone know why or how to solve it?</p>