p>The <code>at</code> method returns an instance of a <a href="scalar/Scalar.html" class="extype" name="org.saddle.scalar.Scalar">org.saddle.scalar.Scalar</a>, which behaves
much like an <code>Option</code>; it can be either an instance of <a href="scalar/NA$.html" class="extype" name="org.saddle.scalar.NA">org.saddle.scalar.NA</a> or a
<a href="scalar/Value.html" class="extype" name="org.saddle.scalar.Value">org.saddle.scalar.Value</a> case class:</p><pre>f.at(<span class="num">0</span>, <span class="num">