function  L2_mesh_plot (inc_e, inc_p)
% Copyright 2010, J.E. Akin.  All rights reserved.
%  ------------------------------------------------------
%  Matlab program to calculate & plot 2-D FE meshes
%  ------------------------------------------------------

% c_x    = x coordinates of nod_per_el line polygon
% c_y    = y coordinates of nod_per_el line polygon
% inc_e  = increment in element numbers on plot, if > 0
% inc_p  = increment in node numbers on plot, if > 0
% msh_typ_nodes   = connectivity list for elements, nt x nod_per_el
% loop   = corners for nod_per_el line polygon
% lab_p  = 1, if node points are circled
  lab_p  = 0;
% nod_per_el = Nodes per element
% np     = Number of Points
% nt     = Number of elements
% pre_e  = Element items before connectivity list
  pre_e  = 0 ;
% pre_p  = Nodal items before coordinates
% msh_bc_xyz = Nodal coordinates (with preceeding data)
% t_x    = x coordinates of nod_per_el corners
% t_y    = y coordinates of nod_per_el corners
% x_bar  = x-centroid of each element
% xy     = Coordinates of points, np x 2
% y_bar  = y-centroid of each element

%    Read coordinate file and connectivity file
%    integer bc code, real xy pairs for np points (pre_p = 1)

  if ( nargin == 1 )
    inc_p = 0;
  end % if
  
%    Set control data: number of points
  load msh_bc_xyz.tmp ;  pre_p = 1;
  %b pre_p = 0  %b para.e subset only
  np = size (msh_bc_xyz,1) ;   % number of nodal points  
  nt=(np-1)/2 ;  % number of elements if sequential
  nod_per_el = 3 ;
  ns = size (msh_bc_xyz,2) - pre_p ;   % dimension of space
  if ( np == 0 )
    error ('Error missing file msh_bc_xyz.tmp')
  end % if error
  fprintf ('Read %g mesh coordinate pairs \n', np)
  % fprintf ('       x        y \n')

  x (np)      = 0.       ;       % pre-allocate array x
  y (np)      = 0.       ;       % pre-allocate array y

  % msh_bc_xyz has: pre_p items then: x, y
  x = msh_bc_xyz (1:np, (pre_p+1)) ; % extract x column of xy
  if ( ns >= 2)
    y = msh_bc_xyz (1:np, (pre_p+2)) ; % extract y column of xy
  else
    y (1:np) = 0. ;
  end % if 1D

%    Set control data: number elements
  load  msh_typ_nodes.tmp ; % nod_per_el nodes per element
  nt = size (msh_typ_nodes,1) ;          % number of elements in mesh
  nod_per_el = size (msh_typ_nodes,2) - pre_e -1 ;% nodes per elem
  fprintf ('Read %g elements connections \n', nt)
  if ( nod_per_el ~= 2 )
    error ('This is not a mesh of 3 node line elements')
  end % if
  
%    Initialize plots
  xmax = max (x)      ; xmin = min (x) ;
  ymax = max (y)      ; ymin = min (y) ;
  xdiff = xmax - xmin ; ydiff = ymax - ymin ;
  if ( ydiff == 0.0 )
    ydiff = 0.5 ; % allow for 1-D mesh (with y == 0)
  end % if no y coordinates
  xmax = xmax + xdiff/10; ymax = ymax + ydiff/10;
  xmin = xmin - xdiff/10; ymin = ymin - ydiff/10;
  clf                               % clear graphics
  axis ([xmin, xmax, ymin, ymax])   % set axes
  axis ('equal')                    % true shape style
  hold on                           % hold image for plots
  grid                              % add grid dots
  xlabel ('X')                      % add label
  ylabel ('Y')                      % add label
  title  (['FE Mesh Geometry: ', int2str(nt), ...
           ' L2 Elements, ', int2str(np),' Nodes'])   
 
%      Plot input mesh elements & label them
 %b  true_L2_plot (x, y) ;
  n_poly = 8 ;
  x_el = zeros (n_poly, 1) ; y_el = zeros (n_poly, 1) ;
  for it = 1:nt  ;

%      Extract element connectivity
    t_nodes = msh_typ_nodes (it, (pre_e+2):(nod_per_el+pre_e+1));
    t_x  = x (t_nodes) ;         % x at those nodes, only
    t_y  = y (t_nodes) ;         % y at those nodes, only
    e_text = sprintf ('    (%i)', it); % offset # from pt
    text (t_x(2), t_y(2), e_text)     % Plot element number
    plot (t_x,t_y)

  end % for it over all elements

%      add the node numbers
  for j = 1:np
    p_text = sprintf (' %i', j) ;
    text (x(j), y(j), p_text) ;
  end % for
  plot ( x, y, 'k*')

extra=0 ;
if (extra == 1 ) % add true quarter circle
  for ang = 1:1:91 ;
    xex (ang) = 4 * cosd(ang-1) ;
    yex (ang) = 4 * sind(ang-1) ;
  end % for    ;   
  plot ( xex, yex, 'r-')
end % if

%       -depsc -tiff            % for an eps version
  % print -dpsc mesh_plot
  hold off
  % fprintf ('Created file L2_mesh_plot.ps \n')
% end of L2_mesh_plot