title: argument must be coercible to non-negative integer in R
body: <p>I am trying to run the following command on my dataset;</p>
  
  <pre><code>   pbad2way(formula = Balance~Occupation+Gender+Occupation:Gender, data = 
  plxsell, est= "mom", nboot= 5000)
  </code></pre>
  
  <p>name of dataset is plxsell
  Balance, Occupation, Gender are the columns</p>
  
  <p>but i am receiving following error;</p>
  
  <p>Error in FUN(X[[i]], ...) : 
    argument must be coercible to non-negative integer
  In addition: Warning message:
  In FUN(X[[i]], ...) : first element used of 'length.out' argument</p>
  
  <p>Please help.</p>
  
  <p>Thanks
  Akhil</p>