Here is the function
DirichletMatrix.m and here is
the script that I used to test it.
Here is the function
NeumannMatrix1.m and here is
the script that I used to test it.
Here is the function
NeumannMatrix2.m and here is
the script that I used to test it.
Here is the function
NeumannMatrix3.m and here is
the script that I used to test it.