s="ot">TRUE</span>)
m<span class="op">$</span>L1 &lt;-<span class="st"> </span><span class="kw">factor</span>(m<span class="op">$</span>L1, <span class="dt">labels=</span><span class="kw">c</span>(<span class="st">&quot;glass&quot;</span>, <span class="st">&quot;metal&quot;</span>, <span class="st">&quot;air&quot;</span>))
<span class="kw">str</span>(m)</code></pre></div>
<pre><code>## 'data.frame':    12000 obs. of  5 variables:
##  $ x       : num  0 -0.802 -1.603 -2.405 -3.206 ...
##  $ variable: Factor 