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<h4>fht</h4>
<pre>protected&nbsp;double[]&nbsp;fht(double[]&nbsp;x)
                throws <a href="../../../../../org/apache/commons/math3/exception/MathIllegalArgumentException.html" title="class in org.apache.commons.math3.exception">MathIllegalArgumentException</a></pre>
<div class="block">The FHT (Fast Hadamard Transformation) which uses only subtraction and
 addition. Requires <code>N * log2(N) = n * 2^n</code> additions.

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