title: Issues with simulating a seasonal ARIMA model
body: <p>I am trying to generate simulations from a seasonal arima model using the forecast package in R via the following command:</p>
  
  <pre><code>simulate(model_temp)
  </code></pre>
  
  <p>where <code>model_temp</code> is the result of applying the <code>arima()</code> function to my observed time series, and with which, incidentally, I specified the model to be an ARIMA(2,1,2)(0,1,2)[12] model.</p>
  
  <p>However, when I attempt this, I get the following error:</p>
  
  <pre><code>Error in diffinv.vector(x, lag, differences, xi) :
    NA/NaN/Inf in foreign function call (arg 1) 
  </code></pre>
  
  <p>Can anybody please explain why this is the case (and how to avoid this problem)?</p>
  
  <p>I should further add, that I know that the model that I applied and resulting in the fit of <code>model_temp</code> is not the model that generated the series, but nevertheless, I would still like to generate simulations from that model (or any other model for that matter).</p>
  
  <p>Lastly, is it possible to generate simulations from a seasonal ARIMA model by just specifying the ar, d, ma, sar, sd, sma and sigma parameters and without having first created an object of the correct ARIMA type?</p>
  
  <p>Thank you for any help,</p>
  
  <p>Jonathan</p>