= contour(X,Y,Z,[.1,.2,.3,.4,.5,.6,.7,.8,.9],<span class="string">'--'</span>);
clear <span class="string">X</span> <span class="string">Y</span> <span class="string">Z</span> <span class="string">C</span>
hold <span class="string">off</span>;
xlabel(<span class="string">'x_1'</span>);
ylabel(<span class="string">'x_2'</span>);
hold <span class="string">off</span>

m = size(data,1);  <span class="comment">% number of baskets, including 0,1</span>

<span class="comment">% add preference data</span>
Pweak = z