function varargout = logde(t,y,flag)
% LOGDE Logistic differential equation
% 
% Stiffness Demonstration:
%   >> tspan=[0 100]; y0 = 0.1; options = odeset('Stats','on');
%   >> [t,y]=ode23('logde',tspan,y0,options);
%   >> plot(t,y),grid,axis([0 100 0.98 1.02])
%   >> h = diff(t); figure, plot(h')

if nargin < 3
	flag = '';
end
%
switch flag
	case ''
		varargout{1} = f(t,y);
  case 'jacobian'
		varargout{1} = jacobian(t,y);
	otherwise
   error(['Unknown flag ''' flag '''.']);
end
% 
function dy = f(t,y)
  dy = y - y.^2;
%
function dfdy = jacobian(t,y)
  dfdy = 1 - 2*y;