function dydt = vanderpol_deriv ( t, y )

%*****************************************************************************80
%
%% vanderpol_deriv() returns the right hand side of vanderpol_ode().
%
%  Licensing:
%
%    This code is distributed under the MIT license.
%
%  Modified:
%
%    05 November 2020
%
%  Author:
%
%    John Burkardt
%
%  Input:
%
%    real T, Y(2), the arguments of the derivative.
%
%  Output:
%
%    real DYDT(2), the value of the derivative.
%
  [ mu, t0, y0, tstop ] = vanderpol_parameters ( );

  u = y(1);
  v = y(2);

  dudt = v;
  dvdt = mu * ( 1.0 - u.^2 ) .* v - u;

  dydt = [ dudt; dvdt ];

  return
end

