ils</p>
<p>The probability density function (pdf) is,</p><pre>pdf(x; lambda, x &gt; 0) = exp(-lambda x) / Z
Z = 1 / lambda
</pre>

<p>where <code>rate = lambda</code> and <code>Z</code> is the normalizing constant.</p>
<p>The Exponential distribution is a special case of the Gamma distribution,
i.e.,</p><pre><span class='fu'><a href='https://rdrr.io/r/stats/Exponential.html'>Exponential</a></span><span class='op'>(</span><span class='va'>rate</span><span class='op'>)</span> <span class='op'>=</span> <span c