annotation></semantics></math>
is the number of observations with a nonzero weight.</p>
<div class="sourceCode" id="cb8"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">x</span> <span class="op">&lt;-</span> <span class="fl">1</span><span class="op">:</span><span class="fl">100</span></span>
<span><span class="va">w</span> <span class="op">&lt;-</span> <span class="fl">1</span><span class="op">:</span><span class="fl">100</span></span>
<span><span class="fu"><a href="htt