The ODES Function 

Save in a text file with the name odes.m

function [x,y] = odes(ydot,interval, y0, h)

% A replacement for MATLAB's ode45 for Octave

% Written by A.O. Hausknecht Spring 2010

x0  = interval(1); % The minimum x-value

x1  = interval(2); % The maximum x-value

x = x0:h:x1; 

% Generate an approximate solution for the differential

% equation with the initial condition y(x0)= y0.

y = lsode(ydot,[y0],x); 

hold on; % Enable plot overlay so plots will be combined

% Generate a vector of x-values using a setsize h = 0.1

% Plot the solution as a curve

size=2; % linewidth and marker size

plot(x,y,'linewidth', size);

% Overlay a the solution points

plot(x,y,'*', 'markersize', size+1);

% Overlay a the solutions initial point in red

plot(x0, y0,'+r','markersize',size+2);

hold off; % Disable plot overlay

% Use the transpose operator to the row vector of

% x-values into a column vector (to match MATLAB's ode45).

x = x'; 

end

Last Updated On: 3/8/10