function [ n_data, x, fx ] = log10_values ( n_data )

%*****************************************************************************80
%
%% LOG10_VALUES returns some values of the logarithm 10 function.
%
%  Discussion:
%
%    In Mathematica, the function can be evaluated by:
%
%      Log10[x]
%
%  Licensing:
%
%    This code is distributed under the GNU LGPL license.
%
%  Modified:
%
%    15 March 2010
%
%  Author:
%
%    John Burkardt
%
%  Reference:
%
%    Milton Abramowitz, Irene Stegun,
%    Handbook of Mathematical Functions,
%    National Bureau of Standards, 1964,
%    ISBN: 0-486-61272-4,
%    LC: QA47.A34.
%
%    Stephen Wolfram,
%    The Mathematica Book,
%    Fourth Edition,
%    Cambridge University Press, 1999,
%    ISBN: 0-521-64314-7,
%    LC: QA76.95.W65.
%
%  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 X, the argument of the function.
%
%    Output, real FX, the value of the function.
%
  n_max = 20;

  fx_vec = [ ...
   -5.0000000000000000000, ...
   -2.0000000000000000000, ...
   -1.0000000000000000000, ...
   -0.69897000433601880479, ...
   -0.52287874528033756270, ...
   -0.39794000867203760957, ...
   -0.30102999566398119521, ...
   -0.22184874961635636749, ...
   -0.15490195998574316929, ...
   -0.096910013008056414359, ...
   -0.045757490560675125410, ...
    0.000000000000000000000, ...
    0.30102999566398119521, ...
    0.47712125471966243730, ...
    0.49714987269413385435, ...
    0.69897000433601880479, ...
    1.0000000000000000000, ...
    1.3010299956639811952, ...
    2.0000000000000000000, ...
    8.0915149771692704475 ];
  x_vec = [ ...
   1.0E-05,  ...
   1.0E-02,  ...
   0.1,  ...
   0.2,  ...
   0.3,  ...
   0.4,  ...
   0.5,  ...
   0.6,  ...
   0.7,  ...
   0.8,  ...
   0.9,  ...
   1.0,  ...
   2.0,  ...
   3.0,  ...
   3.1415926535897932385,  ...
   5.0,  ...
   10.0,  ...
   20.0, ...
   100.0, ...
   123456789.0 ];

  if ( n_data < 0 )
    n_data = 0;
  end

  n_data = n_data + 1;

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

  return
end
