></code></pre></div>
<p>Either as a character, numeric, categorical, or even a Date variable,
it is possible to declare and use special types of missing values,
employing this new object type of class <code class="sourceCode r"><span class="st">"declared"</span></code>.</p>
<p>Factors and <code class="sourceCode r">haven</code> objects have
default coercion methods, but not all types of objects can be
automatically coerced to this class. To meet this possibility, the main
functions <code class="sourceCode r