ODE45 solver solution : subprogram

%
%   Mass-Spring system 
%   ODE45 solver solution
%   ODE45 subprogram
%

function ydot = pms_sol(t,y)

m = 1;                      %  mass of the system in meter
k = 50;                     %  stiffness of the spring (N/m)

yd1 = y(2);
yd2 = -k*y(1)/m;

ydot = [yd1;yd2];