<p>It's used in only 25 questions at the time of writing; the few I looked at all make reference to R's <a href="https://cran.r-project.org/web/packages/plm/index.html" rel="nofollow"><code>plm</code> Linear models for panel data</a> package.</p>

<p>Recall that anyone with over a certain reputation can create new tags&mdash;we can write tag wikis without worrying about their original motivation.</p>
