title: AR(2) considering just the second lag
body: <p>I have this code for an ARIMA(1,1,0)</p>
  <pre><code>arima(Windows(diff(log.variable,1),
                start=1985, perder=c(1,0,0),
                include.means=FALSE, transform.pars=FALSE))
  </code></pre>
  <p>How can I define an AR(2) that considera only the second lag, not the first and the second lag?</p>