Can someone explain to me how to use this file with an example? I found it online. It should convert my matlab matrix output to tecplot. I have a code that produces 4 matrices that need to be plotted in tecplot. Do I run it?

function [] = matrixToTecplotBinaryFile(X,Y,contour,output_file_name,title, varnames)
% Write matlab  matrix into tecplot binary file  *.plt
% adapted from source code URL :
% http://tecplottalk.com/viewtopic.php?t=879&sid=2775b1aff4a1dc523ee890b85ab08f40
%
% output_file_name
% X,Y are x-y coordinates 2D matrix as output from the meshgrid function 
% such that  surf(X,Y,contour) will produce a plot using matlab functions
% contour can be 3D matrix, with dim(3)==var_number except x and y
% title is string for variable
% varnames is cell of string, for single var it still should be {'var'} or 'var'
%--------------------------------------------------
% Comments following match as closely as possible those tecplot binary data format
% HEADER SECTION ->DATA ZONE 
% refer to TECIO lib for cross platform compability:  
% It should work for 32bit/64bit Linux/ and Windows
% For endianness: FOPEN(FILENAME,PERMISSION,MACHINEFORMAT)  : MACHINEFORMAT:  endianess
%------------------------------------------
% %  test 
%N=5
%[X,Y]=meshgrid(1:N,1:N);
%D=ones(N);
%output_file_name='test.plt'
%matrixToTecplotBinaryFile(X,Y,D,output_file_name);
%system('tec360 test.plt');
%
% %test 3D mat by: test_matrixToTecplotBinaryFile.m
%------------------------------------------------
% plt -> matlab?
% load the *.plt is too complicate, using tecplot to export *CVS file, 
% let matlab to import the CVS text file, the file size may be huge. 
%
%from scipy.io import matlab
%mat=matlab.loadmat('file.mat')

if nargin <4
    error('please specify at least X,Y,contour,file_name ');
end

if nargin ==4
    title='test output';
    varnames={'var'};
end
%--------
x_name = 'Px';
y_name = 'subImage';
if ischar(varnames)
    matvarlist = {varnames};
else
    matvarlist = varnames;
end

%---------
MultipleVarEnable=false;
dim=size(contour);
var_data_cell={};

if length(dim)==2
    var_count=2+1;
    var_data_cell={X,Y,contour};
else if length(dim)==3
      var_count=2+dim(3); 
      MultipleVarEnable=true;
      % built the var data cell array to simplify store
      var_data_cell={X,Y};
      for di=3:var_count
            var_data_cell{di}=contour(:,:,di-2);
      end
     % msgbox('write multiple var is not implmented'); return;
    end
end

%assert( size(var_data_cell{1}) == size(var_data_cell{3})  );

%
PrecisoinByCountOfInt32=2;   % float64
MatrixVarFloatTypeStr ='float64';

%-----------------------------------
fid_out = fopen(output_file_name,'w');  %should  be 'wb'
if fid_out <0
    disp('Fail to open the file to write, check permission and path format \n');
end

% ---------i. magic number ???--
magic_number = '#!TDV112';
char_hold = char(magic_number);
l_max = max(size(char_hold));
for ii =1:1:l_max
    fwrite(fid_out,char_hold(ii),'char');
end

%------- ii. Integer value of 1.
dummy_int32 = 1;
fwrite(fid_out,dummy_int32,'int32');
% iii. Title and variable names.
% filetype
dummy_int32 = 0;   % end of object
fwrite(fid_out,dummy_int32,'int32');

%-------iii write title and terminate with a null char
plt_write_string(fid_out, title);

% Number of variables
dummy_int32 = var_count;
fwrite(fid_out,dummy_int32,'int32');
%variable names just give 3 names

plt_write_string(fid_out, x_name);
plt_write_string(fid_out, y_name);
% additional var name list
for i=1:length(matvarlist)
    plt_write_string(fid_out, matvarlist{i});
end

% ---------iv. Zones
% write zone marker float32 = 299.0
dummy_float32 = single(299.0);
fwrite(fid_out,dummy_float32,'float32');

% write zone name 'data zone' and nul
zone_name = 'Data zone';
plt_write_string(fid_out, zone_name);

% parent zone = 0 (no parent zone) int32
dummy_int32 = -1;
fwrite(fid_out,dummy_int32,'int32');

% strand ID suggested as zero from old calls
dummy_int32 = 0;
fwrite(fid_out,dummy_int32,'int32');

% solution_time
solution_time = pi;
fwrite(fid_out,solution_time,'float64');

% not used set to -1 (int32)
dummy_int32 = -1;
fwrite(fid_out,dummy_int32,'int32');

% zone_type (ordered = 0)
%
zone_type = 0;
fwrite(fid_out,zone_type,'int32');

% var_location (0 = all data at nodal points)
% 
var_location = 0;
fwrite(fid_out,var_location,'int32');

% are raw local 1-to-1 face neighbors supplied (must be false for ordered)
% flase = 0 (int32)
dummy_int32 = 0;
fwrite(fid_out,dummy_int32,'int32');

% No. of miscellaneous user defined face neighbor connections
NoOfUserDefinedNeighbourConn = 0;
fwrite(fid_out,NoOfUserDefinedNeighbourConn,'int32');

% ordered zone var 3 int32s for num points i -j -k
[Imax,Jmax] =size(X);
Kmax = 1;   
fwrite(fid_out,Imax,'int32');
fwrite(fid_out,Jmax,'int32');
fwrite(fid_out,Kmax,'int32');

% No auxilary data pairs
dummy_int32 = 0;
fwrite(fid_out,dummy_int32,'int32');

%--------------------- v. Geometries ???
% looks like we can get away without it

EOH_MARKER=single(357.0);
fwrite(fid_out, EOH_MARKER ,'float32')

%--------------------------------------------------
% II. DATA SECTION
% i for both ordered and fe
% zone marker = 299.0
dummy_float32 = single(299.0);
fwrite(fid_out,dummy_float32,'float32');

% specify data format for plt file 64 bit floats for each var int32 = 2 per
for i=1:var_count
   fwrite(fid_out,PrecisoinByCountOfInt32,'int32');
end

% no passive variables
dummy_int32 = 0;
fwrite(fid_out,dummy_int32,'int32');

% no variable sharing
dummy_int32 = 0;
fwrite(fid_out,dummy_int32,'int32');

% zone number to share connectivity with
dummy_int32 = -1;
fwrite(fid_out,dummy_int32,'int32');

%--------------% data----------
% write data in the right order
% reshape matrices to 1D vector
var_vector_cell={};
for di=1:var_count
    var_vector_cell{di}= reshape(var_data_cell{di},1,(Imax*Jmax));
end

% get data minima and maxima after reshape to call min max once per set
for di=1:var_count
    C=var_vector_cell{di};
    min_C = min(C);  % for reshaped 1D vecter
    max_C = max(C);
    fwrite(fid_out,min_C,MatrixVarFloatTypeStr);
    fwrite(fid_out,max_C,MatrixVarFloatTypeStr);
end

% write data
for di=1:var_count
   fwrite(fid_out,var_vector_cell{di},MatrixVarFloatTypeStr);
end

% ii. specific to ordered
    % null as misc user def connections = 0

% iii. specific to Finite element format, therefore not generated

% ------------end of file
fclose(fid_out);

return 

%======================================

function l= plt_write_string(fid_out,string)
% return the size_t of int32
char_hold = int32(string);
l_max = max(size(char_hold));
for ii =1:1:l_max
    fwrite(fid_out,char_hold(ii),'int32');
end
dummy_int32 =0;
fwrite(fid_out,dummy_int32,'int32');
l=l_max+1;

function l= plt_write_numeric(fid_out,numeric1Dvector, numeric_type_str)
% for one dim vector only , dummy nul int32 is not appened
l_max = length(numeric1Dvector);
fwrite(fid_out,numeric1Dvector, numeric_type_str);

% for ii =1:1:l_max
%     fwrite(fid_out,numeric1Dvector(ii), numeric_type_str);
% end
l=l_max+1;

function l= plt_write_dummy(fid_out)
% mean empty
dummy_int32 =0;
fwrite(fid_out,dummy_int32,'int32');
l=1;

Answer 1

[Walter Roberson]

It is documented:

% X,Y are x-y coordinates 2D matrix as output from the meshgrid function 
% such that  surf(X,Y,contour) will produce a plot using matlab functions
% contour can be 3D matrix, with dim(3)==var_number except x and y
% title is string for variable
% varnames is cell of string, for single var it still should be {'var'} or 'var'

If your 4 plots share the same x and y then your contour array can be M x N x 4 where M x N is the X Y size.