variate with a linear effect on the log intensities, using the same techniques as in the previous chapter.</p></li>
<li><p>Use <code>pci</code> to fit a model with a categorical “time period” covariate on all intensities.</p></li>
<li><p>Extract the imputed dataset that <code>msm</code> constructs in (2), by using <code>model.frame</code>. Use this dataset to build more refined models with categorical time period variables.</p></li>
</ol>
<p>In each case, AIC could be used to compare models with differe