function  result_on_const_y (i_p, y_p, filename, row) %CL
%b function  result_on_const_y (i_p, y_p, filename)
% 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_p  = Nodal items before coordinates
% pre_r  = Nodal items before results %CL
% row    = row number where cord & connectivity start, 1 or 2 %CL
% 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
  pre_e  = 0 ;
  pre_p = 1;
  pre_r = 0 ; %CL

  % fprintf ('Begin component value carpet plots: \n')
  if ( nargin == 0 )
    i_p = 0 ; y_p = 0. ; filename = ['null'] ; row = 1 ; %CL
  elseif ( nargin == 1 )
    y_p = 0. ; filename = ['null'] ; row = 1 ; %CL
  elseif ( nargin == 2 )
    filename = ['null'] ; row = 1 ; %CL
  elseif ( nargin == 3 )
    row = 1 ; %CL
  elseif ( nargin == 4 ) %CL
    pre_e =  0; %CL
    pre_r = 2 ; %CL
  end % if no arguments
  less = row - 1 ; %CL

%    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)
  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 
  nt = nt - less ; %CL
  nod_per_el = size (msh_typ_nodes,2) - pre_e -1 ; % nodes per elem
  Col_1 = pre_e+2 ; %CL
  Col_2 = nod_per_el+pre_e+1 ; %CL

  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

%                set constants

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

%   create a file for combining graphs (3 items per row)
  %b fid = fopen('graphs_on_y.dat','a+') ;
  if ( filename(1:4) ~= ['null'] )
    fid = fopen(filename,'a+') ;
  else
    fid = 0 ;
  end % if file given
  ymdhms = fix(clock) ;
  if ( fid > 0 )
    fprintf (fid,'%g %g  %g \n', BOG, i_p, y_p ); % -8 i_p y_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
  end % if


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

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

%    Cite max, min values
  if ( given > 0 )
     [V_X, L_X] = max (z(1:given)) ;
     [V_N, L_N] = min (z(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)) ;
   zmax = max (z(1:given))       
   zmin = min (z(1:given)) 
   if ( zmin == zmax )
     zmax = zmin + (xmax - xmin)/50 ;
     zmin = zmin - (xmax - xmin)/50 ;
   end % if

%b add delimiter to graph file for possible multiple graphs
   if ( fid > 0 )
     fprintf (fid,'%g %g %g \n', EOG, zmin, zmax );
   end % if fid

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

   hold on                           % hold image for plots
   xlabel (['X for ', int2str(given),' Points at Y = ', ...
            num2str(y_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), z(1:given),'k*')
   grid
   [y(1:given),i_sort] = sort( x(1:given) ) ;
   plot(x(i_sort), z(i_sort), 'k-');

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