function  result_on_const_yz (i_p, y_p, z_p, out_name)
% Copyright 2000, J.E. Akin.  All rights reserved.
%  ------------------------------------------------------
%   If i_p = 0, show RMS value
%  ------------------------------------------------------

% c_x    = x coordinates of nod_per_el line polygon
% c_y    = y coordinates of nod_per_el line polygon
% msh_typ_nodes   = connectivity list for elements, nt x nod_per_el
% loop   = corners for nod_per_el line polygon
% 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
% t_y    = y coordinates of nod_per_el corners
  BOG = -8 ; % 1st of graph tag to sepreate file saves
  EOG = -9 ; % end of graph tag to sepreate file saves

format short g

  % fprintf ('Begin component value carpet plots: \n')
  if ( nargin == 0 )
    i_p = 0 ; y_p = 0. ; z_p = 0.; out_name = ['null'] ;
  elseif ( nargin == 1 )
    y_p = 0. ; z_p = 0.; out_name = ['null'] ;
  elseif ( nargin == 2 )
    z_p = 0.; out_name = ['null'] ;
  elseif ( nargin == 3 )
    out_name = ['null'] ;
  end % if no arguments

%    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 < 2 )
    error ('This is not a 2D mesh')
  end % if not 2D 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

  load node_results.tmp
  nr = size (node_results, 1);
  if ( nr == 0 )
    error ('Error missing file node_results.tmp')
  end % if error
  max_p = size (node_results, 2) ; % number of columns
  fprintf ('Read %g nodal result values \n', nr)
  fprintf ('     with %g components each \n', max_p)
  if ( i_p > (max_p+1) ) 
    error ('i_p > available data')
  end % if error

  x (np)      = 0.       ;       % pre-allocate array x
  y (np)      = 0.       ;       % pre-allocate array y
  z (np)      = 0.       ;       % pre-allocate array z
  R (np)      = 0.       ;       % pre-allocate array R

%                set constants

  % msh_bc_xyz has: pre_p items then: x, y
  y = msh_bc_xyz (1:np, (pre_p+2)) ; % extract y column
  ymax = max (y) ; ymin = min (y) ; diff = ymax - ymin ;
  tol = abs ( diff / (10 * np) ) ;
  z = msh_bc_xyz (1:np, (pre_p+3)) ; % extract z column

%   create a file for combining graphs (3 items per row)
  %b fid = fopen('graphs_on_y.dat','a+') ;
  if ( out_name(1:4) ~= ['null'] )
    fid = fopen(out_name,'a+') ;
  else
    fid = 0 ;
  end % if file given
  ymdhms = fix(clock) ;
  fprintf (fid,'%g %g  %g \n', BOG, y_p, z_p ); % -8 y_p z_p
  fprintf (fid,'%g %g  %g \n', ymdhms (1:3)    ); % yr mon day
  fprintf (fid,'%g %g  %g \n', ymdhms (4:6)    ); % hr min sec

  given = 0 ;
  for j = 1:np ; % check all nodes
    if ( abs (y(j) - y_p) <= tol ) % found a point
      if ( abs (z(j) - z_p) <= tol ) % found a point
       given = given + 1 ;
       x (given) = msh_bc_xyz (j, (pre_p+1)) ; % extract y

       if ( i_p >= 1 )
       %b if ( i_p >= 1 & i_p <=3 )
         R(given) = node_results(j, i_p) ;
       %b elseif ( i_p == 4 ) % Von Mises Stress
         %b root_2 = sqrt (2.) ;
         %b temp = (node_results (j, 1) ...
              %b -  node_results (j, 2))^2 ...
              %b +  node_results (j, 1)^2 ...
              %b +  node_results (j, 2)^2 ...
              %b +  node_results (j, 3)^2 * 6 ;
         %b R (given) = sqrt ( temp ) / root_2 ;
       else % i_p = 0, get root mean sq
         R (given) = sqrt(sum(node_results(j,1:max_p).^2));
       end % if get RMS value
       fprintf (fid,'%g %g %g \n', given, x(given), R(given) );
     end % if tol on z
   end % if tol on y
  end % for j

%    Cite max, min values
  if ( given > 0 )
     [V_X, L_X] = max (R(1:given)) ;
     [V_N, L_N] = min (R(1:given)) ;
     fprintf ('Max value is %g at node %g \n', V_X, L_X)
     fprintf ('Min value is %g at node %g \n', V_N, L_N)
     if ( V_X == V_N ) % constant
       V_X = V_X + 2;
     end % if
  else
     error 'No nodes found for given position'
  end % if given 

%    Initialize plots
   xmax = max (x(1:given))      ; xmin = min (x(1:given)) ;
   Rmax = max (R(1:given))      ; Rmin = min (R(1:given)) ;
   if ( Rmin == Rmax )
     Rmax = Rmin + (xmax - xmin)/50 ;
     Rmin = Rmin - (xmax - xmin)/50 ;
   end % if
% Rmin=-0.10
% Rmax=5.0 

%b add delimiter to graph file for possible multiple graphs
  fprintf (fid,'%g %g %g \n', EOG, Rmin, Rmax );

   clf                               % clear graphics
   axis ([xmin, xmax, Rmin, Rmax])   % set axes
   %b axis ('square')

   hold on                           % hold image for plots
   xlabel (['X for ', int2str(given),' Points at Y = ', ...
            num2str(y_p), ', Z = ', num2str(z_p), ...
            '  (', int2str(nt),' Elements, ', ...
            int2str(np),' Nodes)'])
   if ( i_p > 0 )
     ylabel (['Component\_',int2str(i_p),'  (max = ', ...
     num2str(V_X), ', min = ', num2str(V_N), ')'])
     title(['Nodal FEA Solution Component\_',int2str(i_p), ...
        ',  (', int2str(nod_per_el), ' nodes per element)'])
   else % i_p = 0, get root mean sq
     ylabel (['Nodal RMS Solution Value (max = ', ...
     num2str(V_X), ', min = ', num2str(V_N), ')'])
     title(['Nodal RMS Flux Value'])            
   end % if get RMS value
   plot(x(1:given), R(1:given),'k*')
   grid
   [y(1:given),i_sort] = sort( x(1:given) ) ;
   plot(x(i_sort), R(i_sort), 'k-');

%% end % if show labels
%       -depsc -tiff            % for an eps version
  %b print ('-dpsc', ['result_', int2str(i_p), '_on_yz'])
  hold off
  %b v_text = ['Created result_', int2str(i_p), '_on_yz.ps'] ;
  %b fprintf (1,'%s', v_text) ; fprintf (1, ' \n' )
% end of result_on_const_yz