function  quiver_2d_frame_load_mesh (i_p, scale) 
% Copyright 2006, J.E. Akin.  All rights reserved.
%  ------------------------------------------------------
%  plot of 3-D FE resultant load vectors, on 2D mesh,
% with increment of inc_v, include mesh if mesh=1
%  ------------------------------------------------------
inc_v = 1;
mesh=1;
% 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
% inc_v  = increment in vector plot, default = 1
% 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;
% length = maximum length of arrows, in scaled x,y units
% nod_per_el = Nodes per element
% np     = Number of Points
% nt     = Number of elements
% pre_e  = Element items before connectivity list
% pre_p  = Nodal items before coordinates
% msh_bc_xyz = Nodal coordinates (with preceeding data)
% scale  = standard Matlab scale argument, default 1.0
% 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

  pre_e  = 0 ;
  pre_p  = 1 ;
  pre_r  = 0 ;
  if ( nargin == 0 )
    i_p = 1 ; scale = 1.  ;   % the default scale
  elseif ( nargin == 1 )
    scale = 1.  ;   % the default scale  L
  end % if
  row = 1 ; less = row - 1 ; %CL
  fprintf ('Using a scale of %g and vector increment of %g \n', ...
            scale, inc_v)

%    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  
  np = np - less ;   %CL
  fprintf ('Read %g mesh coordinate pairs \n', np)
% fprintf ('       x        y \n')
  
%    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 
  nt = nt - less ; %CL
  nod_per_el = size (msh_typ_nodes,2) - pre_e -1; % nodes per element
  fprintf ('Read %g elements connections \n', nt)
  Col_1 = pre_e+2 ; %CL
  Col_2 = nod_per_el+pre_e+1 ; %CL

% read 2-d resultant vector at nodes
  load node_resultant.tmp

%       Set control data: number of Reaction points
  npg = size(node_resultant,1) ; % resultant pts w vectors
  npg = npg - pre_r ; %CL
  if ( npg <= 0 )
    error ('Error: missing file node_resultant.tmp')
  end % if error
  fprintf ('Read %g nodal resultant sets \n', npg)
  nf = size(node_resultant,2)-3 ;  % load components
  if ( nf ~= 3 ) % vectors not meaningful
    fprintf ('Read %g components instead of 3 \n', nf)
  end % if vector data

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

%    Mesh Range Alone
  % msh_bc_xyz has: pre_p items then: x, y
  %b x = msh_bc_xyz (1:np, (pre_p+1)) ; % extract x column of xy
  %b y = msh_bc_xyz (1:np, (pre_p+2)) ; % extract y column of xy
  x = msh_bc_xyz (row:(np+less), (pre_p+1)) ; % extract x  %CL
  y = msh_bc_xyz (row:(np+less), (pre_p+2)) ; % extract y %CL

  gxmax = max (x)      ; gxmin = min (x) ;
  gymax = max (y)      ; gymin = min (y) ;
  gxdiff = gxmax - gxmin ; gydiff = gymax - gymin ;
  if ( gydiff == 0.0 )
    gydiff = 0.5 ; % allow for 1-D mesh (with y == 0)
  end % if no y coordinates

%     Vector Values
  g_x  = zeros (npg, 1) ; g_y  = zeros (npg, 1) ;
  g_dx = zeros (npg, 1) ; g_dy = zeros (npg, 1) ;
  for j = 1:npg                          ;
    node  = node_resultant (j, 1)        ; 
    DOF   = node_resultant (j, 2)        ; 
    value = node_resultant (j, 3)        ; 
    g_x (j)  = x (node)                  ; % position
    g_y (j)  = y (node)                  ; % position
    if ( DOF == 1 )
      g_dx (j) =  value                  ; % x load
    elseif ( DOF == 2 )
      g_dy (j) =  value                  ; % y load
    elseif ( DOF == 3 )
      m_dy (j) =  value                  ; % moment
      m_dx (j) =  0                      ;
    else
      error('Frame DOF ~= 1, 2, or 3')
    end % if
  end % for
  g_sq = sqrt (g_dx.^2 + g_dy.^2) ;
  big  = max (g_sq)  ; % magnitude

  largest = 0.0  ;
%     Scale flux     vectors
  if ( big > largest ) largest = big;

  xmax = gxmax + gxdiff/10 ; ymax = gymax + gydiff/10 ; % keep
  xmin = gxmin - gxdiff/10 ; ymin = gymin - gydiff/10 ; % keep
% xmax = gxmax + gxdiff/20 ; ymax = gymax + gydiff/20 ;
% xmin = gxmin - gxdiff/20 ; ymin = gymin - gydiff/20 ;

  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 Coordinate at ', int2str(np),' Nodes'])     
  ylabel (['Y Coordinate on ', int2str(nt),' Elements (with ', ...
           int2str(nod_per_el), ' nodes) '])
  title (['FEA 2-D Resultant Load Vectors, max = ', ...
          num2str(largest),' (Scale = ', num2str(scale),')']) 

%      Select element type details
   [loop] = get_El_Loop (nod_per_el) ;

%%      Plot input mesh points & label them
%  if (lab_p == 1)                   % plot all points
%    plot (x, y, 'b.')               % mark each node
%  end % if show labels

%    Show 20 nodes and 10 elements
  inc_p = floor(np/10) ; inc_e = floor(nt/5) ;
  if (inc_p == 0 ) 
    inc_p = np - 1 ;
  end % if inc_p
  if (inc_e == 0 ) 
    inc_e = nt - 1 ;
  end % if inc_e
%    Show all if a small mesh
  if ( np <= 20 )
    inc_p = 1 ;
  end % if np
  if ( nt <= 10 )
    inc_e = 1 ;
  end % if nt
inc_p=1;
inc_e=1;

  if (inc_p > 0)                      % plot node numbers
    for i = 1:inc_p:np                % convert to string
      p_text = sprintf ('  %g', i);   % offset # from pt
      text (x(i), y(i), p_text)       % plot pt number
    end % for all points
  end % if show labels
% disp (' ')

 if ( mesh == 1 )
%    Loop over all elements
  for it = 1:nt  ;

%      Extract corner connectivity 
    %b t_nodes = msh_typ_nodes (it, (pre_e+2):(nod_per_el+pre_e+1)); 
    t_nodes = msh_typ_nodes ((it+less), Col_1:Col_2 ) ; %CL

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

%      Get the centroid
    x_bar (it) = sum (t_x' )/nod_per_el ;
    y_bar (it) = sum (t_y' )/nod_per_el ;

%      Plot this polygon
    c_x  = t_x (loop) ;       % x for nod_per_el line polygon
    c_y  = t_y (loop) ;       % y for nod_per_el line polygon
    plot (c_x, c_y, 'g-')     % plot nod_per_el lines, in blue
  end % for over all elements
 
%%    Finish the plots with polygon numbers
%  if (inc_e > 0)                     % plot elem number, inclined
%    % plot (x_bar, y_bar, 'g.')        % centroid of each element
%    for i = 1:inc_e:nt               % convert to string
%      t_text = sprintf ('  %g', i);  % offset # from pt
%      text (x_bar(i), y_bar(i), t_text, 'Rotation', 45) % incline
%    end % for all polygons
%  end % if show labels
end % if mesh plot

%  ---------------- Now add the vectors to the mesh --------------
  quiver (g_x, g_y, g_dx, g_dy, scale)

%       -depsc -tiff            % for an eps version
  %b print -dpsc quiver_resultant_vec_mesh
hold off
%b fprintf ('Created file 2d_frame_load_mesh.ps \n')    
end % quiver_resultant_vec_mesh 
%end quiver_2d_frame_load_mesh (i_p, scale)