function [ n_data, x, fx ] = debye1_values ( n_data )

%*****************************************************************************80
%
%% DEBYE1_VALUES returns some values of Debye's function of order 1.
%
%  Discussion:
%
%    The function is defined by:
%
%      DEBYE1(x) = 1 / x * Integral ( 0 <= t <= x ) t / ( exp ( t ) - 1 ) dt
%
%    The data was reported by McLeod.
%
%  Licensing:
%
%    This code is distributed under the GNU LGPL license.
%
%  Modified:
%
%    16 September 2004
%
%  Author:
%
%    John Burkardt
%
%  Reference:
%
%    Allan McLeod,
%    Algorithm 757, MISCFUN: A software package to compute uncommon
%      special functions,
%    ACM Transactions on Mathematical Software,
%    Volume 22, Number 3, September 1996, pages 288-301.
%
%  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 = [ ...
      0.99951182471380889183E+00, ...
      0.99221462647120597836E+00, ...
      0.96918395997895308324E+00, ...
      0.88192715679060552968E+00, ...
      0.77750463411224827642E+00, ...
      0.68614531078940204342E+00, ...
      0.60694728460981007205E+00, ...
      0.53878956907785587703E+00, ...
      0.48043521957304283829E+00, ...
      0.38814802129793784501E+00, ...
      0.36930802829242526815E+00, ...
      0.32087619770014612104E+00, ...
      0.29423996623154246701E+00, ...
      0.27126046678502189985E+00, ...
      0.20523930310221503723E+00, ...
      0.16444346567994602563E+00, ...
      0.10966194482735821276E+00, ...
      0.82246701178200016086E-01, ...
      0.54831135561510852445E-01, ...
      0.32898681336964528729E-01 ];

  x_vec = [ ...
       0.0019531250E+00, ...
       0.0312500000E+00, ...
       0.1250000000E+00, ...
       0.5000000000E+00, ...
       1.0000000000E+00, ...
       1.5000000000E+00, ...
       2.0000000000E+00, ...
       2.5000000000E+00, ...
       3.0000000000E+00, ...
       4.0000000000E+00, ...
       4.2500000000E+00, ...
       5.0000000000E+00, ...
       5.5000000000E+00, ...
       6.0000000000E+00, ...
       8.0000000000E+00, ...
      10.0000000000E+00, ...
      15.0000000000E+00, ...
      20.0000000000E+00, ...
      30.0000000000E+00, ...
      50.0000000000E+00 ];       

  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

