as suffix (separated by underdcore "_").</p>
    </div>

    <div id="ref-examples">
    <h2>Examples</h2>
    <div class="sourceCode"><pre class="sourceCode r"><code><span class="r-in"><span><span class="co"># Get US census data on population and households for 2000 and 2010 censuses on a uniform geography</span></span></span>
<span class="r-in"><span><span class="co"># based on census tracts.</span></span></span>
<span class="r-in"><span><span class="kw">if</span> <span class="op">(</span><span class="cn"