function  fiber_heat_flux_overlay (xmin, xmax, ymin, ymax, scale, Pts_wide)
% Copyright 2007, J.E. Akin.  All rights reserved.
%  ------------------------------------------------------
%             bare minimum borders
%  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 type & connectivity list
% pre_p  = Nodal items before coordinates
% LIST1DN_001 = Nodal coordinates (with preceeding data)
% t_x    = x coordinates of nod_per_el corners
% t_y    = y coordinates of nod_per_el corners
% xy     = Coordinates of points, np x 2

if ( nargin < 6 ) 
  Pts_wide = 2
end % if
if ( nargin < 5 )
  scale = 1
end % if
pre_e  = 0  ;
pre_p = 0;
hold on

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

%    Set control data: number of points
  load LIST1DN_001.tmp ;  
  np = size (LIST1DN_001,1) ;   % number of nodal points  
  ns = size (LIST1DN_001,2) - pre_p ;   % dimension of space
  if ( np == 0 )
    error ('Error missing file LIST1DN_001.tmp')
  %b else
    %b fprintf ('using fiber data LIST1DN_001.tmp')
  end % if error

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

  % LIST1DN_001 has: pre_p items then: x, y
  x = LIST1DN_001 (1:np, (pre_p+1)) ; % extract x  %CL
  y = LIST1DN_001 (1:np, (pre_p+2)) ; % extract y %CL
  
%    Set control data: number elements & nodes_per_element
  load  LIST1DE_001.tmp ; % nod_per_el nodes per element
  nt = size (LIST1DE_001,1);           % number of elements 
  if ( nt == 0 )
    error ('Error missing file LIST1DE_001.tmp')
  end % if error
  nod_per_el = size (LIST1DE_001,2) - pre_e ; % nodes per element

  t_nodes (nod_per_el) = 0 ;    % Optional pre-allocation
  t_x (nod_per_el) = 0 ;        % Optional pre-allocation
  t_y (nod_per_el) = 0 ;        % Optional pre-allocation
  c_x (nod_per_el + 1) = 0 ;    % Optional pre-allocation
  c_y (nod_per_el + 1) = 0 ;    % Optional pre-allocation
  loop (nod_per_el + 1) = 0 ;   % Optional pre-allocation
 
  load seg_flux_001.tmp ; % centroid & flux vector
  ncg = size(seg_flux_001, 1) ; % number of centroids
  if ( ncg == 0 )
    error ('Missing data file seg_flux_001.tmp')
  else
    fprintf ('Using fiber data seg_flux_001.tmp \n')
  end % if
  xcg = seg_flux_001(:,1) ;
  ycg = seg_flux_001(:,2) ;
  xhf = seg_flux_001(:,3) ;
  yhf = seg_flux_001(:,4) ;

  flux = sqrt ( xhf.^2 + yhf.^2 ) ;
  max_flux = max(flux) ;
  min_flux = min(flux) ;
  fprintf ('Largest fiber flux = %g \n', max_flux)

%                set constants
  [loop] = get_El_Loop (nod_per_el) ;

if (Pts_wide > 0 ) % show fibers too
  for it = 1:nt  ;

    t_nodes = LIST1DE_001 (it, 1:2 ) ; 

%      Extract corner coordinates
    t_x  = x (t_nodes) ;         % x at those nodes, only
    t_y  = y (t_nodes) ;         % y at those nodes, only

%      Plot this segment
    c_x  = t_x (loop) ;       % x for nod_per_el line polygon
    c_y  = t_y (loop) ;       % y for nod_per_el line polygon
 
    %b plot (c_x, c_y, 'y-', 'LineWidth',Pts_wide) 
    plot (c_x, c_y, 'g-', 'LineWidth',Pts_wide) 
    %b plot (c_x, c_y, 'k-', 'LineWidth',Pts_wide) 

  end % for over all elements
end % if Pts_wide > 0
  %b XXX xhf = xhf/10 ; yhf = yhf/10 ;
scale = 4
  quiver (xcg, ycg, xhf, yhf, scale)
 
%       -depsc -tiff            % for an eps version
% end fiber_heat_flux_overlay