comment">// fill v with noisy data.</span>
<span class="keyword">double</span> <span class="identifier">spacing</span> <span class="special">=</span> <span class="number">0.001</span><span class="special">;</span>
<span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">differentiation</span><span class="special">::</span><span class="identifier">discrete_lanczos_derivati