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

%*****************************************************************************80
%
%% POISSON_CDF_VALUES returns some values of the Poisson CDF.
%
%  Discussion:
%
%    CDF(X)(A) is the probability of at most X successes in unit time,
%    given that the expected mean number of successes is A.
%
%    In Mathematica, the function can be evaluated by:
%
%      Needs["Statistics`DiscreteDistributions`]
%      dist = PoissonDistribution [ a ]
%      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.
%
%    Daniel Zwillinger,
%    CRC Standard Mathematical Tables and Formulae,
%    30th Edition, CRC Press, 1996, pages 653-658.
%
%  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, real A, the parameter of the function.
%
%    Output, integer X, the argument of the function.
%
%    Output, real FX, the value of the function.
%
  n_max = 21;

  a_vec = [ ...
     0.02E+00, ...
     0.10E+00, ...
     0.10E+00, ...
     0.50E+00, ...
     0.50E+00, ...
     0.50E+00, ...
     1.00E+00, ...
     1.00E+00, ...
     1.00E+00, ...
     1.00E+00, ...
     2.00E+00, ...
     2.00E+00, ...
     2.00E+00, ...
     2.00E+00, ...
     5.00E+00, ...
     5.00E+00, ...
     5.00E+00, ...
     5.00E+00, ...
     5.00E+00, ...
     5.00E+00, ...
     5.00E+00 ];

  fx_vec = [ ...
     0.9801986733067553E+00, ...
     0.9048374180359596E+00, ...
     0.9953211598395555E+00, ...
     0.6065306597126334E+00, ...
     0.9097959895689501E+00, ...
     0.9856123220330293E+00, ...
     0.3678794411714423E+00, ...
     0.7357588823428846E+00, ...
     0.9196986029286058E+00, ...
     0.9810118431238462E+00, ...
     0.1353352832366127E+00, ...
     0.4060058497098381E+00, ...
     0.6766764161830635E+00, ...
     0.8571234604985470E+00, ...
     0.6737946999085467E-02, ...
     0.4042768199451280E-01, ...
     0.1246520194830811E+00, ...
     0.2650259152973617E+00, ...
     0.4404932850652124E+00, ...
     0.6159606548330631E+00, ...
     0.7621834629729387E+00 ];

  x_vec = [ ...
     0, 0, 1, 0, ...
     1, 2, 0, 1, ...
     2, 3, 0, 1, ...
     2, 3, 0, 1, ...
     2, 3, 4, 5, ...
     6 ];

  if ( n_data < 0 )
    n_data = 0;
  end

  n_data = n_data + 1;

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

  return
end