% initsys.m 
% Used to enter necessary information for 1st order ODE systems. Needed by 
% PPLANE2D.M, SYS3PLOT.M. 

global A B g eqn_name tvec x0vec s y 

N=20; 

%%%%% 
% User entered info/choices 
t0=0; tf=2;  % Initlal and final t-values 
x0vec=[3,2]; % Initial x(t)-values (one for each system equation). 
initax=[-2.5,2.5,-2.5,2.5]; % Plot window axis ranges 
A=[1,1; 4,1];  % RHS matrix for x' = Ax system. Contains coeff. for linear terms 
B=[];   % Matrix of coeff. for nonlinear terms 
x1symb='2*exp(3*t)+exp(-t)';  % if 2nd order ODE, this is symbolic solution 
x2symb='4*exp(3*t)-2*exp(-t)';   % if 2nd order ODE, this is symbolic derivative 
eqn_name='cclin';     % MATLAB function name to be used by ODE45 
 symbolicplot='solutions'; 
% symbolicplot='phase'; 
% symbolicplot='eigenvals'; 
% symbolicplot=''; 
%%%%%

tvec=[t0, tf]; 
eigvals=eig(A); 
[s,y]=ode45(eqn_name,tvec,x0vec);