function [ n_data, k, fx ] = bessel_j0_zero_values ( n_data )

%*****************************************************************************80
%
%% BESSEL_J0_VALUES returns some zeros of the J0 Bessel function.
%
%  Licensing:
%
%    This code is distributed under the GNU LGPL license.
%
%  Modified:
%
%    04 January 2016
%
%  Author:
%
%    John Burkardt
%
%  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 K, the index of the zero.
%
%    Output, real FX, the value of the function.
%
  n_max = 30;

  fx_vec = [ ...
    2.40482555769577276862163187933E+00, ... 
    5.52007811028631064959660411281E+00, ... 
    8.65372791291101221695419871266E+00, ... 
    11.7915344390142816137430449119E+00, ...
    14.9309177084877859477625939974E+00, ...
    18.0710639679109225431478829756E+00, ...
    21.2116366298792589590783933505E+00, ...
    24.3524715307493027370579447632E+00, ...
    27.4934791320402547958772882346E+00, ...
    30.6346064684319751175495789269E+00, ...
    33.7758202135735686842385463467E+00, ...
    36.9170983536640439797694930633E+00, ...
    40.0584257646282392947993073740E+00, ...
    43.1997917131767303575240727287E+00, ...
    46.3411883716618140186857888791E+00, ...
    49.4826098973978171736027615332E+00, ...
    52.6240518411149960292512853804E+00, ...
    55.7655107550199793116834927735E+00, ...
    58.9069839260809421328344066346E+00, ...
    62.0484691902271698828525002646E+00, ...
    65.1899648002068604406360337425E+00, ...
    68.3314693298567982709923038400E+00, ...
    71.4729816035937328250630738561E+00, ...
    74.6145006437018378838205404693E+00, ...
    77.7560256303880550377393718912E+00, ...
    80.8975558711376278637721434909E+00, ...
    84.0390907769381901578796383480E+00, ...
    87.1806298436411536512618050690E+00, ...
    90.3221726372104800557177667775E+00, ...
    93.4637187819447741711905915439E+00 ];

  k_vec = [ ...
     1, ...
     2, ...
     3, ...
     4, ...
     5, ...
     6, ...
     7, ...
     8, ...
     9, ...
    10, ...
    11, ...
    12, ...
    13, ...
    14, ...
    15, ...
    16, ...
    17, ...
    18, ...
    19, ...
    20, ...
    21, ...
    22, ...
    23, ...
    24, ...
    25, ...
    26, ...
    27, ...
    28, ...
    29, ...
    30  ];

  if ( n_data < 0 )
    n_data = 0;
  end

  n_data = n_data + 1;

  if ( n_max < n_data )
    n_data = 0;
    k = 0;
    fx = 0.0;
  else
    k = k_vec(n_data);
    fx = fx_vec(n_data);
  end

  return
end

