function xStiffODEs
% xStiffODEs.m
% Demonstrate how to solve a set of simultaneous ODE stiff equations
%
%   Author: HUANG Huajiang
%   Copyright 2003 UNILAB Research Center, 
%   East China University of Science and Technology, Shanghai, PRC
%   $Revision: 1.0 $  $Date: 2003/02/24 $

clear all
clc

y0 = [0 1];
% [x1,y1] = ode45(@f,[0  100],y0)
[x2,y2] = ode23s(@f,[0  100],y0)

% ------------------------------------------------------------------
function dydx = f(x,y)      % Define simultaneous ODE equations
dy1dx = 0.04*(1-y(1))-(1-y(2))*y(1)+0.0001*(1-y(2))^2; 
dy2dx = -1e4*dy1dx + 3000*(1-y(2))^2;
dydx = [dy1dx; dy2dx];