function fx = quartic ( x )

%% QUARTIC evaluates a function defined by a sum of fourth powers.
%
%  Modified:
%
%    28 February 2008
%
%  Author:
%
%    John Burkardt
%
%  Reference:
%
%    R ONeill,
%    Algorithm AS 47:
%    Function Minimization Using a Simplex Procedure,
%    Applied Statistics,
%    Volume 20, Number 3, 1971, pages 338-345.
%
%  Parameters:
%
%    Input, real X(10), the argument.
%
%    Output, real FX, the value of the function.
%
  fx = 0.0;

  for i = 1 : 10
    fx = fx + x(i) * x(i) * x(i) * x(i);
  end