function  contour_qp_d_vec_mesh (i_p, row) %CL
Pts_wide=2;
% Copyright 2004, J.E. Akin.  All rights reserved.
% plot element Gauss point Dvec i_p magnitude

% x,y   ==  nodal coordinates of the FEA
% f     ==  nodal solution of the FEA
% X,Y   ==  nodal coordinates of the structured square mesh
% F     ==  interpolated solution for the structured square mesh
% NX    ==  number of nodes in x-direction for structured mesh 
% NY    ==  number of nodes in y-direction for structured mesh
% pre_e  = Element items before connectivity list
% pre_p  = Nodal items before coordinates
% pre_r  = Nodal items before results %CL
% row    = row number where cord & connectivity start, 1 or 2 %CL

pre_e  = 0 ;
pre_p = 1;
if ( nargin == 0 )
  i_p = 0 ; row = 1 ;
elseif ( nargin == 1 )  %CL
  row = 1 ; %CL
elseif ( nargin == 2 )  %CL
  pre_e = 0 ;  %CL
end % if no arguments
less = row - 1 ; %CL

load msh_bc_xyz.tmp;
np = size (msh_bc_xyz, 1);
np = np - less ;   %C
fprintf ('Read %g mesh coordinate pairs \n', np)
ns = size (msh_bc_xyz,2) - pre_p ;   % space dimension
if ( ns < 2 )
  error ('This is not a 2D mesh')
end % if not 2D data

load  msh_typ_nodes.tmp ; % nod_per_el nodes per element
nt         = size (msh_typ_nodes,1);           % number of elements
nt = nt - less ; %C
fprintf ('Read %g element topology sets \n', nt)
if ( nt <= 0 ) %CL
  error ('Error missing file msh_typ_nodes.tmp')
end % if error
nod_per_el = size (msh_typ_nodes,2) - pre_e -1 ; % nodes per element
Col_1 = pre_e+2 ; %CL
Col_2 = nod_per_el+pre_e+1 ; %CL

load qp_xy_d_vector.tmp; % x,y followed by grad list
ng = size (qp_xy_d_vector, 1) ;     % count points
nf = size (qp_xy_d_vector, 2) - 2;  % count components
fprintf ('Read %g Gauss point locations \n', ng)
fprintf ('with %g grad components \n', nf)
if ( ng == 0 )
  error ('Error missing file qp_xy_d_vector.tmp')
end % if error
if ( nf <= 0 )
  error ('Error, no grads in file qp_xy_d_vector.tmp')
end % if error
if ( i_p > nf )
  error ('Error, requested component not present')
end % if error

% NX, NY = 31 are default values, these can be altered by user
NX = 51; NY = 51;

x = qp_xy_d_vector (:, 1);
y = qp_xy_d_vector (:, 2);
 
if ( i_p > 0 )
  f =  qp_xy_d_vector (:, (i_p + 2)) ;
else
  for j = 1:ng
    f(j) = sqrt ( sum(qp_xy_d_vector (j, 3:(nf+2)).^2) ) ;
  end % for ng points
end % which component

xlin = linspace (min(x), max(x), NX);
ylin = linspace (min(y), max(y), NY);
[X, Y] = meshgrid (xlin, ylin);
F = griddata (x, y, f, X, Y, 'cubic');

clf
c = contour (X,Y,F,'LineWidth',Pts_wide);
clabel (c);
hold on
grid

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

%   get mesh x,y (not QP x,y)
  %b x_m = msh_bc_xyz (:, 2); y_m = msh_bc_xyz (:, 3);
  x_m = msh_bc_xyz (row:(np+less), (pre_p+1)) ; % extract x  %C
  y_m = msh_bc_xyz (row:(np+less), (pre_p+2)) ; % extract y %C

%    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_m (t_nodes) ;         % x at those nodes, only
    t_y  = y_m (t_nodes) ;         % y at those nodes, only

%      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)           % plot nod_per_el lines
  end % for over all elements

xlabel (['X: ', int2str(nt),' Elements'])
ylabel (['Y: ', int2str(np),' Nodes'])
% xlabel ('X'); ylabel ('Y');
if ( i_p > 0 )
  title (['FEA QP D Vector Component\_', int2str(i_p), ...
          ': at ', int2str(ng), ' Gauss Points']);
else
  title (['FEA QP D Vector RMS Value at ', ...
          int2str(ng), ' Gauss Points'])
end % which component
%       -depsc -tiff            % for an eps version
  %bprint ('-dpsc', ['contour_qp_d_vec_mesh_', int2str(i_p)])
  hold off
  %bv_text = ['Created contour_qp_d_vec_mesh_', int2str(i_p), '.ps'];
  %bfprintf (1,'%s', v_text) ; fprintf (1, ' \n' )

% end of contour_qp_d_vec_mesh