title: L1 norm contour plot in matlab
body: <p>I am trying to plot the level set of L1 norm in matlab. But it is not at all working, and I am stuck.  Any help ?</p>
  
  <pre><code>x = linspace(-1,1,10);
  y = linspace(-1,1,10);
  [xm,ym] = meshgrid(x,y);
  z = sum(abs(xm-ym));
  surfc(x,y,z)
  </code></pre>