    int&nbsp;length)
                throws <a href="../../../../../../../org/apache/commons/math3/exception/MathIllegalArgumentException.html" title="class in org.apache.commons.math3.exception">MathIllegalArgumentException</a></pre>
<div class="block">Returns the sum of the natural logs of the entries in the specified portion of
 the input array, or <code>Double.NaN</code> if the designated subarray
 is empty.
 <p>
 Throws <code>MathIllegalArgumentException</code> if the array is null.</p>
 <p>
 See <a hr