title: Shading an area boundered by a curve
body: <p>What would be the easiest way to lightly shade (or hatch; or anything to set it different from the rest) an area in a plot(), below a curve y=x^2, for example ?</p>
  
  <pre><code>x = 0:pi/10:2*pi;  
  y = x.^2.;
  plot(x,y);
  </code></pre>