function  elem_qp_flux_1d_graph ()
% Copyright 2000, J.E. Akin.  All rights reserved.
%  ------------------------------------------------------
%  Matlab graph of error estimate   value at mesh nodes
%  ------------------------------------------------------

% c_x    = x coordinates of nod_per_el line element
% msh_typ_nodes   = connectivity list for elements, nt x nod_per_el
% loop   = corners for nod_per_el line element
% 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
  pre_p = 1;
% msh_bc_xyz = Nodal coordinates (with preceeding data)
% t_x    = x coordinates of nod_per_el corners

  fprintf ('Begin element qp flux graph: \n')

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

%    Set control data: number of points
  np = size (msh_bc_xyz,1) ;   % number of nodal points  
  fprintf ('Read %g mesh coordinate pairs \n', np)
  ns = size (msh_bc_xyz,2) - pre_p ;   % space dimension
  if ( ns ~= 1)
    error ('This is not a 1D mesh')
  end % if not 1D data
  
%    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)

%       Read new Gauss locations & flux component
  load el_qp_xyz_fluxes.tmp ; % x, du/dx

%       Set control data: number of gauss points
  npg = size(el_qp_xyz_fluxes,1) ; % quadrature pts w vectors
  if ( npg == 0 )
    error ('Error: missing file el_qp_xyz_fluxes.tmp')
  end % if error
  fprintf ('Read %g Gauss x coord & flux sets \n', npg)
  nf = size(el_qp_xyz_fluxes,2) - ns;  % flux components
  if ( nf ~= 1  ) % vectors not meaningful
    fprintf ('Read %g flux components instead of 1 \n', nf)
    fprintf ('Using only first component \n')
    nf = 1 ;
    %b fprintf ('Use contour_el_fluxes or smooth_el_fluxes instead \n')
    %b error ('Error: These are not 1-D data')
  end % if

  x (np)      = 0.       ;       % pre-allocate array x
  y (np)      = 0.       ;       % pre-allocate array y
  % 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) = 0 ;        % Optional pre-allocation
  c_y (nod_per_el) = 0 ;        % Optional pre-allocation
  g_x(npg)   = 0.       ;       % pre-allocate position array
  g_dx(npg)  = 0.       ;       % pre-allocate flux     array

%     FE Flux Values
  d_x(2) = 0. ; d_y(2)  = 0. ; % vector ends on paper

% Gauss points are always inside the mesh geometry
  g_x  = el_qp_xyz_fluxes(:,1)  ; % position
  g_dx = el_qp_xyz_fluxes(:,2)  ; % flux

%                set constants
  loop = [1:nod_per_el] ; % default to sequential order

  % msh_bc_xyz has: pre_p items then: x, y
  x = msh_bc_xyz (1:np, (pre_p+1)) ; % extract x column

%    Cite max, min values
  [V_X, L_X] = max (g_dx) ;
  [V_N, L_N] = min (g_dx) ;
  fprintf ('Max value is %g \n', V_X)
  fprintf ('Min value is %g \n', V_N)
  null (1:np) = V_N ;

%    Initialize plots
   xmax = max (x)      ; xmin = min (x) ;
   ymax = V_X          ; ymin = V_N     ;
   if ( ymax == ymin )
     if ( abs (ymax) > 0 )
       ymax = ymax + abs (ymax)/20. ;
       ymin = ymin - abs (ymin)/20. ;
     end % if
   end % if
   clf                               % clear graphics
 % ymax= 1.0 
 % ymin= 0.0
   axis ([xmin, xmax, ymin, ymax])   % set axes

   hold on                           % hold image for plots
   xlabel ('X, Node number at 45 deg, Element number at 90 deg')
   title(['Flux Value at Element Quadrature Points:   ', ...
            int2str(nt),' Elements, ', int2str(np),' Nodes'])
   ylabel (['Flux  (max = ', ...
   num2str(V_X), ', min = ', num2str(V_N), ')'])

  plot (g_x, g_dx, 'ko')

% plot node points on axis
  for i = 1:np
    t_text = sprintf ('   %g', i);  % offset # from pt
    text (x(i), null(i), t_text, 'Rotation', 45) % incline
  end % for all
  plot (x, null, 'k*')
  grid
 
% label max min points 
  v_text = sprintf ('---min') ;
  text  (g_x(L_N), V_N, v_text) ;
  v_text = sprintf ('---max') ;
  text  (g_x(L_X), V_X, [v_text]) ;

%       -depsc -tiff            % for an eps version
  %bprint ('-dpsc', ['elem_qp_flux_1d_graph'])
  hold off
  %bv_text = ['Created elem_qp_flux_1d_graph.ps'] ;
  %bfprintf (1,'%s', v_text) ; fprintf (1, ' \n' )
% end of elem_qp_flux_1d_graph