function  contour_qp_source_on_mesh (i_p)
Pts_wide=2;
% Copyright 2000, J.E. Akin.  All rights reserved.
% plot element Gauss point flux i_p magnitude as a surface 
% convert any type of mesh to a structured square mesh

% 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

if ( nargin == 0 )
  i_p = 0 ;
end % if no arguments

load msh_bc_xyz.tmp;
np = size (msh_bc_xyz, 1);
fprintf ('Read %g mesh coordinate pairs \n', np)
pre_p = 1;
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

pre_e  = 0 ;
load  msh_typ_nodes.tmp ; % nod_per_el nodes per element
nt         = size (msh_typ_nodes,1);           % number of elements
if ( nt == 0 )
  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

load el_qp_xyz_sources.tmp; % x,y followed by flux list
ng = size (el_qp_xyz_sources, 1) ;     % count points
nf = size (el_qp_xyz_sources, 2) - 2;  % count components
if ( ng == 0 )
  error ('Error missing file el_qp_xyz_sources.tmp')
end % if error
if ( nf <= 0 )
  error ('Error, no fluxes in file el_qp_xyz_sources.tmp')
end % if error

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

x = el_qp_xyz_sources (:, 1);
y = el_qp_xyz_sources (:, 2);
 
if ( i_p > 0 )
  f =  el_qp_xyz_sources (:, (i_p + 2)) ;
else
  for j = 1:ng
    f(j) = sqrt ( sum(el_qp_xyz_sources (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)
  x_m = msh_bc_xyz (:, 2); y_m = msh_bc_xyz (:, 3);

%    Loop over all elements
  for it = 1:nt  ;

%      Extract corner connectivity
    t_nodes = msh_typ_nodes (it, (pre_e+2):(nod_per_el+pre_e+1));

%      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 (['Matlab Smoothed FEA QP Source  Component\_', ...
          int2str(i_p), ': at ', int2str(ng), ' Gauss Points']);
else
  title (['Matlab Smoothed FEA QP Source RMS Value at ', ...
          int2str(ng), ' Gauss Points'])
end % which component
%       -depsc -tiff            % for an eps version
  %bprint ('-dpsc', ['contour_qp_source_on_mesh_', int2str(i_p)])
  hold off
  %bv_text = ['Created contour_qp_source_on_mesh_', int2str(i_p), '.ps'];
  %bfprintf (1,'%s', v_text) ; fprintf (1, ' \n' )

% end of contour_qp_source_on_mesh