tract_data(d2-d1)).</p>
</dd></dl>

<dl class="py function">
<dt class="sig sig-object py" id="pySurf.data2D.sum_data">
<span class="sig-prename descclassname"><span class="pre">pySurf.data2D.</span></span><span class="sig-name descname"><span class="pre">sum_data</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">d1</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">d2</span></span></em>, <em class="sig-param"><span class="n"><span 