function dydt = stetter_deriv ( t, y )

%*****************************************************************************80
%
%% stetter_deriv evaluates the right hand side of the Stetter ODE.
%
%  Discussion:
%
%    y' = lambda(t) * y
%
%    where lambda(t) is periodic, piecewise linear, and discontinuous.
%
%  Licensing:
%
%    This code is distributed under the MIT license.
%
%  Modified:
%
%    05 March 2021
%
%  Author:
%
%    John Burkardt
%
%  Input:
%
%    real T, Y: the time and solution value.
%
%  Output:
%
%    real DYDT: the derivative value.
%
  lambda = stetter_lambda ( t );
%
%  Y might be a vector.
%  If so, we need to ensure that it is a column vector.
%
  y = y(:);

  dydt = lambda .* y;

  return
end

