function [ n_data, a, b, x, fx ] = f_cdf_values ( n_data )

%*****************************************************************************80
%
%% F_CDF_VALUES returns some values of the F CDF test function.
%
%  Discussion:
%
%    In Mathematica, the function can be evaluated by:
%
%      Needs["Statistics`ContinuousDistributions`"]
%      dist = FRatioDistribution [ dfn, dfd ]
%      CDF [ dist, x ]
%
%  Licensing:
%
%    This code is distributed under the GNU LGPL license.
%
%  Modified:
%
%    29 September 2004
%
%  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.
%
%  Parameters:
%
%    Input/output, integer N_DATA.  The user sets N_DATA to 0 before the
%    first call.  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.
%
%    Output, integer A, integer B, the parameters of the function.
%
%    Output, real X, the argument of the function.
%
%    Output, real FX, the value of the function.
%
  n_max = 20;

  a_vec = [ ...
    1, ...
    1, ...
    5, ...
    1, ...
    2, ...
    4, ...
    1, ...
    6, ...
    8, ...
    1, ...
    3, ...
    6, ...
    1, ...
    1, ...
    1, ...
    1, ...
    2, ...
    3, ...
    4, ...
    5 ];

  b_vec = [ ...
     1, ...
     5, ...
     1, ...
     5, ...
    10, ...
    20, ...
     5, ...
     6, ...
    16, ...
     5, ...
    10, ...
    12, ...
     5, ...
     5, ...
     5, ...
     5, ...
     5, ...
     5, ...
     5, ...  
     5 ];

  fx_vec = [ ...
     0.5000000000000000E+00, ...
     0.4999714850534485E+00, ...
     0.4996034370170990E+00, ...
     0.7496993658293228E+00, ...
     0.7504656462757382E+00, ...
     0.7514156325324275E+00, ...
     0.8999867031372156E+00, ...
     0.8997127554259699E+00, ...
     0.9002845660853669E+00, ...
     0.9500248817817622E+00, ...
     0.9500574946122442E+00, ...
     0.9501926400000000E+00, ...
     0.9750133887312993E+00, ...
     0.9900022327445249E+00, ...
     0.9949977837872073E+00, ...
     0.9989999621122122E+00, ...
     0.5687988496283079E+00, ...
     0.5351452100063650E+00, ...
     0.5143428032407864E+00, ...
     0.5000000000000000E+00 ];

  x_vec = [ ...
      1.00E+00, ...
      0.528E+00, ...
      1.89E+00, ...
      1.69E+00, ...
      1.60E+00, ...
      1.47E+00, ...
      4.06E+00, ...
      3.05E+00, ...
      2.09E+00, ...
      6.61E+00, ...
      3.71E+00, ...
      3.00E+00, ...
     10.01E+00, ...
     16.26E+00, ...
     22.78E+00, ...
     47.18E+00, ...
      1.00E+00, ...
      1.00E+00, ...
      1.00E+00, ...
      1.00E+00 ];

  if ( n_data < 0 )
    n_data = 0;
  end

  n_data = n_data + 1;

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

  return
end