ield(N,<span class="string">'r'</span>), <span class="comment">% no apparent resistivities</span>
0148     <span class="keyword">if</span> ~isfield(N,<span class="string">'rho'</span>)&amp;&amp;isfield(N,<span class="string">'u'</span>)&amp;&amp;isfield(N,<span class="string">'i'</span>), N.rho=N.u./N.i; <span class="keyword">end</span>
0149     <span class="keyword">if</span> isfield(N,<span class="string">'rho'</span>), N.r=N.rho.*N.k; <span class="keyword">end</span>
0150 <span class="keyword">end</span>