% initn.m 
% Used to enter RHS and necessary information for 1st order ODEs that 
% will be solved via Euler's Method and/or RK4. Needed by EULPLOT.M 
% RK4PLOT.M, NUMPLOT.M 

N=20; 
ftx='2*t*x';    % Enter ODE as string variable; e.g., '2*t*x' 
eulerfcn='x+h*(2*t*x)';  % RHS for Euler's method 
hvec=[.5,.25,.1,.01];  % Vector of step sizes to investigate 
%hvec=10;
[minh,minhindex]=min(hvec);  % ID of min step size and location in hvec 
t0=-2; tf=2; x0=1;   % Initial values/conditions 
t=tf; x=x0; h=max(hvec);  % Initializations to determine starting initax 
xmin=min([x0,eval(eulerfcn)]); xmax=max([x0,eval(eulerfcn)]); 
initax=[t0,tf,xmin,xmax];  % To set reasonable starting window 
ax=initax;