title: un-log a times series while using the package forecast
body: <p>Hello I use the package forecast in order to do times-series prevision. <strong>I would like to know how to un-log</strong> a series on the final forecast plot. With the forecast package I don't know how to un-log my series. Here is an example:</p>
  
  <pre><code>library(forecast)
  data &lt;- AirPassengers
  data &lt;- log(data) #with this AirPassengers data not nessesary to LOG but with my private data it is...because of some high picks...
  ARIMA &lt;- arima(data, order = c(1, 0, 1), list(order = c(12,0, 12), period = 1)) #Just a fake ARIMA in this case... 
  plot(forecast(ARIMA, h=24)) #but my question is how to get a forecast plot according to the none log AirPassenger data
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/GIPX6.png" alt="enter image description here"></p>
  
  <p><em>So the image is logged. I want to have the same ARIMA modell but witht the none loged data.</em></p>