[問題] 想請教有關matlab內建的ballode

[anikishawn (哲平)]

function ballode
%BALLODE  Run a demo of a bouncing ball.

tstart = 0;
tfinal = 30;
y0 = [0; 20];
refine = 4;
options = odeset('Events',@events,'OutputFcn', @odeplot,...
                 'OutputSel',1,'Refine',refine);
             set(gca,'xlim',[0 30],'ylim',[-25 25]);
box on
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.
  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 time step is the length of
  % the last valid time step, so use it for faster computation.
  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 only


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這是個物理現象 球的拋體運動
水平速度為0
垂直速度為20

是把y(t)=(-9.8*t^2)/2

拆成一組常微分方程
y_1'(t)=y_2(t)
y_2'(t)=-9.8

我知道的部分就這些


想問請程式碼的意思

像options裡面那些函數所表示的意思




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※ 編輯: anikishawn      來自: 140.123.61.208       (11/06 15:48)
→ anikishawn:不好意思 我是學純數學的 對程式不是很懂 還請包含
→ ejialan:help odeset 他有對每個設定做解釋
→ anikishawn:謝謝哦 我昨天使用過help去找了 看了很久的時間 應該是
→ anikishawn:這個code在做什麼 表達什麼了
→ anikishawn:^知道