title: isosurface function MATLAB usage
body: <p>Hi can any one give me a simple example of how to use the isosurface function in MATLAB. 
  The example given if you type <code>help isosurface</code> is quite confusing. Searching on google did not help as no one gives simple examples anywhere. All of them use predefined functions like 
  <code>flow</code>. </p>
  
  <p>For starters, suppose i have points <code>(x,y,z)</code> where z=0 and at each point I define a constant 
  function <code>f(x,y,z)=6</code>. So if I use the isosurface function on the isovalue <code>6</code> I would like MATLAB to give me a 3d plot with the XY plane highlighted in some colour, say green. </p>