title: R forecast function error
body: <p>I am trying to use the forecast function (forecast package in R) and running into problem.  Consider the following example:</p>
  
  <pre><code>library(forecast)
  fit=arima(WWWusage,order=c(1,1,1))
  fcast=forecast(fit)
  plot(fcast)
  </code></pre>
  
  <p>At the forecast step, I am getting the error message:</p>
  
  <pre><code>Error in .forecast.transform(x, xv, a, h, 1) : 
    argument "xv" is missing, with no default
  </code></pre>
  
  <p>This happens even if I replace <code>arima</code> by <code>Arima</code> or <code>auto.arima</code> functions in the <code>forecast</code> package.  </p>