21 357 ...</span>
<span class="r-out co"><span class="r-pr">#&gt;</span>  $ Days    : num  0 1 2 3 4 5 6 7 8 9 ...</span>
<span class="r-out co"><span class="r-pr">#&gt;</span>  $ Subject : Factor w/ 18 levels "308","309","310",..: 1 1 1 1 1 1 1 1 1 1 ...</span>
<span class="r-in"><span><span class="kw"><a href="https://rdrr.io/r/base/library.html" class="external-link">require</a></span><span class="op">(</span><span class="va"><a href="https://lattice.r-forge.r-project.org/" class="external-link">lattice<