function mfile heat6.m calculates the solution of the heat equation in
      two space dimensions which is the sum of two Gaussian humps. No boundaries.

      function mfile heat7.m calculates the solution of a boundary value 
      problem for the heat equation in two space dimensions by summing the
      eigenfunction expansion. 

      radial.m is a short program which sets up polar coordinates in the
      unit disk, and plots z = r.  It can be modified to plot other radial
      functions, such as the Bessel functions.