">]</span>, grid <span class="op">=</span> <span class="fl">1</span><span class="op">:</span><span class="fl">24</span><span class="op">)</span></span></code></pre></div>
<p>Then, we extract the scalar response variable, i.e. the mean of
<code>NO2</code> at each observation:</p>
<div class="sourceCode" id="cb2"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">y</span> <span class="op">&lt;-</span> <span class="fu"><a href="https://rdrr.io/r/base/colSums.html" class="exte