function [ indx, nunk ] = indx_set ( nx, ny, node_num )

%% INDX_SET assigns a boundary value index or unknown value index at each node.
%
%  Discussion:
%
%    Every finite element node will is assigned an index which
%    indicates the finite element basis function and its coefficient
%    which are associated with that node.
%
%  Example:
%
%    On a simple 5 by 5 grid, where the nodes are numbered starting 
%    at the lower left, and increasing in X first, we would have the 
%    following values of INDX:
%
%       21  22  23  24  25
%       16  17  18  19  20
%       11  12  13  14  15
%        6   7   8   9  10
%        1   2   3   4   5
%
%  Modified:
%
%    17 May 2005
%
%  Parameters:
%
%    Input, integer NX, NY, the number of elements in the X and Y directions.
%
%    Input, integer NODE_NUM, the number of nodes.
%
%    Output, integer INDX(NODE_NUM), the index of the unknown in the finite 
%    element linear system.
%
%    Output, integer NUNK, the number of unknowns.
%
  nunk = 0;
  in = 0;

  for j = 1 : 2 * ny - 1

    for i = 1 : 2 * nx - 1

      in = in + 1;
      nunk = nunk + 1;
      indx(in) = nunk;

    end
  end