pendulum_period

function pendulum_period
% pendulum waves-寻找合适的摆长
clc;clear;close all
g=10;T=200;
opts=odeset('RelTol',1e-13,'AbsTol',1e-14, ...
    'MaxStep',1e-3,'InitialStep',1e-4, ...
    'Stats','off','Events',@(t,u)evns(t,u));
L=0.8:0.01:2.4;
for ii=1:length(L)
[t,u]=ode45(@(t,u)pw(t,u,g,L(ii)), ...
    [0 T],[pi/6 0],opts);
w(ii)=1/t(end);
end
max(w)
min(w)
L=interp1(w,L,1.28:0.05:2.18);
save matlab.mat L
%% 微分方程与事件函数
function du=pw(~,u,g,L)
du=[u(2);-g/L*sin(u(1))];
function [position,isterminal,direction] = evns(~,u)
position = u(1);isterminal = 1;direction  = -1;