```%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%This script file is to run simulate a bouncy non-
%compression-force spring
%by Andy Ruina on 2/20/97
% Two or three dimensional simulation of a mass on
% a spring that can carry no compression force.

clear all
global k Lzero m g jhat n

k=29; m=1; Lzero=3; g=10; %note the special results if Lzero=0

z0=[2 1 0 0 0 0];  %put 4 or 6 numbers here for a 2D or 3D simulation

n=length(z0)/2;  % n is the number of dimensions 2, or 3

jhat = zeros(1,n); jhat(2) = 1; % jhat is a unit vector in y dir

t0=0; tf=10; tol=1E-4;

[t,z]=ode23('springfn', t0, tf, z0, tol);

%Here are some plotting options: (1), (2), and (3)

% 1) comet is kind of cool
%comet(z(:,1), z(:,2));

% 2) double plot
%subplot(2,1,1)
%plot(z(:,1), z(:,2));   axis('equal') ;
%xlabel('x'); ylabel('y'); title('Andy Ruina plot 2/20/97')
%subplot(2,1,2)
%plot(t,  z(:,2))
%xlabel('t'); ylabel('y')

% 3) 3D Plot
plot3 ( z(:,1), z(:,2), z(:,3) )
axis('equal')
%end of script file
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
```