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function ballode
tstart = 0;
tfinal = 30;
y0 = [0; 20];
refine = 8;
options = odeset('Events',@events,'OutputFcn',@odeplot,'OutputSel',1,...
'Refine',5);
figure;
set(gca,'xlim',[0 30],'ylim',[0 25]);
hold on;
tout = tstart;
yout = y0.';
teout = [];
yeout = [];
ieout = [];
for i = 1:10
% Solve until the first terminal event.
[t,y,te,ye,ie] = ode23(@f,[tstart tfinal],y0,options);
if ishold
hold on
end
% Accumulate output. This could be passed out as output arguments.
nt = length(t);
tout = [tout; t(2:nt)];
yout = [yout; y(2:nt,:)];
teout = [teout; te]; % Events at tstart are never reported.
yeout = [yeout; ye];
ieout = [ieout; ie];
ud = get(gcf,'UserData');
if ud.stop
break;
end
% Set the new initial conditions, with .9 attenuation.
y0(1) = 0;
y0(2) = -.9*y(nt,2);
% A good guess of a valid first timestep is the length of the last valid
% timestep, so use it for faster computation. 'refine' is 4 by default.
options = odeset(options,'InitialStep',t(nt)-t(nt-refine),...
'MaxStep',t(nt)-t(1));
tstart = t(nt);
end
plot(teout,yeout(:,1),'ro')
xlabel('time');
ylabel('height');
title('Ball trajectory and the events');
hold off
odeplot([],[],'done');
% --------------------------------------------------------------------------
function dydt = f(t,y)
dydt = [y(2); -9.8];
% --------------------------------------------------------------------------
function [value,isterminal,direction] = events(t,y)
% Locate the time when height passes through zero in a decreasing direction
% and stop integration.
value = y(1); % detect height = 0
isterminal = -1; % stop the integration
direction = -1; % negative direction
想请教一下 odeset指令的用法 还有events函数是什么意�
