function  contour_n_exact_flux (i_p)
Pts_wide=2;
% Copyright 2000, J.E. Akin.  All rights reserved.
% plot node scp ave of i_p flux component
% convert any type of mesh to a structured square mesh

% The flux gradients are stored as N_R_B flux components
% associated with N_SPACE grident components. Here N_SPACE = 2
% Poisson Eq: U,x,x U,y,x : U,y,x U,y,y :
% Plane stress: e_x,x e_y,x e_xy,x : e_x,y e_y,y, e_xy,y
% or U,x,x U,y,x (U,y,x + U,x,x) : U,x,y U,y,y (U,y,y + U,x,y)

% 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
format short

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 exact_node_flux.tmp; % x,y followed by flux list
ng = size (exact_node_flux, 1) ;     % count points
nf = size (exact_node_flux, 2) ;  % count components
if ( ng == 0 )
  error ('Error missing file exact_node_flux.tmp')
end % if error
if ( nf <= 0 )
  error ('Error, no fluxes in file exact_node_flux.tmp')
else
  fprintf ('%g flux components with 2 gradient components \n', nf/2)
  nf = nf/2  ;
end % if error

% NX, NY = 31 are default values, these can be altered by user
NX = 41; NY = 41;

x = msh_bc_xyz (:, 1+pre_p);
y = msh_bc_xyz (:, 2+pre_p);
 
if ( i_p > 0 ) % then
  f =  exact_node_flux (:, i_p) ;
else % use RMS
   for j = 1:ng
     f(j) = sqrt ( sum(exact_node_flux (j, :).^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

xlabel (['X: ', int2str(nt),' Elements'])
ylabel (['Y: ', int2str(np),' Nodes (', int2str(nod_per_el), ' per Element)'])
if ( i_p > 0 )
  title (['Smoothed Exact Flux Component\_', int2str(i_p)'])  
else
  title (['Smoothed Exact Flux RMS Value '])
end % which component
%       -depsc -tiff            % for an eps version
  %b print ('-dpsc', ['contour_n_exact_flux_', int2str(i_p)])
  hold off
  %b v_text = ['Created contour_n_exact_flux_', int2str(i_p), '.ps'];
  %b fprintf (1,'%s', v_text) ; fprintf (1, ' \n' )

% end of contour_n_exact_flux