function [ n_data, a, x, fx ] = chi_square_cdf_values ( n_data )

%*****************************************************************************80
%
%% chi_square_cdf_values() returns some values of the Chi-Square CDF.
%
%  Discussion:
%
%    In Mathematica, the function can be evaluated by:
%
%      Needs["Statistics`ContinuousDistributions`"]
%      dist = ChiSquareDistribution [ df ]
%      CDF [ dist, x ]
%
%  Licensing:
%
%    This code is distributed under the MIT license.
%
%  Modified:
%
%    14 February 2003
%
%  Author:
%
%    John Burkardt
%
%  Reference:
%
%    Milton Abramowitz and Irene Stegun,
%    Handbook of Mathematical Functions,
%    US Department of Commerce, 1964.
%
%    Stephen Wolfram,
%    The Mathematica Book,
%    Fourth Edition,
%    Wolfram Media / Cambridge University Press, 1999.
%
%  Input:
%
%    integer N_DATA.  The user sets N_DATA to 0 before the first call.
%
%  Output:
%
%    integer N_DATA.  On each call, the routine increments N_DATA by 1, and
%    returns the corresponding data; when there is no more data, the
%    output value of N_DATA will be 0 again.
%
%    integer A, the parameter of the function.
%
%    real X, the argument of the function.
%
%    real FX, the value of the function.
%
  n_max = 21;

  a_vec = [ ...
     1,  2,  1,  2, ...
     1,  2,  3,  4, ...
     1,  2,  3,  4, ...
     5,  3,  3,  3, ...
     3,  3, 10, 10, ...
    10 ];

  fx_vec = [ ...
     0.7965567455405796E-01, ...
     0.4987520807317687E-02, ... 
     0.1124629160182849E+00, ...
     0.9950166250831946E-02, ...
     0.4729107431344619E+00, ... 
     0.1812692469220181E+00, ... 
     0.5975750516063926E-01, ... 
     0.1752309630642177E-01, ... 
     0.6826894921370859E+00, ... 
     0.3934693402873666E+00, ... 
     0.1987480430987992E+00, ... 
     0.9020401043104986E-01, ... 
     0.3743422675270363E-01, ... 
     0.4275932955291202E+00, ... 
     0.6083748237289110E+00, ... 
     0.7385358700508894E+00, ... 
     0.8282028557032669E+00, ... 
     0.8883897749052874E+00, ... 
     0.1721156299558408E-03, ... 
     0.3659846827343712E-02, ... 
     0.1857593622214067E-01 ];

  x_vec = [ ...
     0.01E+00, ... 
     0.01E+00, ...  
     0.02E+00, ... 
     0.02E+00, ... 
     0.40E+00, ... 
     0.40E+00, ... 
     0.40E+00, ... 
     0.40E+00, ... 
     1.00E+00, ... 
     1.00E+00, ... 
     1.00E+00, ... 
     1.00E+00, ... 
     1.00E+00, ... 
     2.00E+00, ... 
     3.00E+00, ... 
     4.00E+00, ... 
     5.00E+00, ... 
     6.00E+00, ... 
     1.00E+00, ... 
     2.00E+00, ... 
     3.00E+00 ];

  if ( n_data < 0 )
    n_data = 0;
  end

  n_data = n_data + 1;

  if ( n_max < n_data )
    n_data = 0;
    a = 0;
    x = 0.0;
    fx = 0.0;
  else
    a = a_vec(n_data);
    x = x_vec(n_data);
    fx = fx_vec(n_data);
  end

  return
end
