Week 3 - Solving second order ODEs

Explanation:- i got error in video that not playing properly but i create images and then convert it into video.

clear all
close all
clc

b=0.05;
g=9.81;
l=1;
m=1;

%initial condition
theta_0 =[0;3];

%time points
t_span = linspace(0,20,100);

%solve ode
[t,results]=ode45(@(t,theta) ode_func(t,theta,b,g,l,m),t_span,theta_0);


ct=1;
for i=1:length(results(:,1));
    x0=0;
    y0=0;
    x1=l*sin(results(i,1));
    y1=-l*cos(results(i,1));
    subplot(5,4,[1,2,3,4,5,6,7,8,9,10,11,12]);
    plot([-1 1],[0 0],'linewidth',4);
    hold on
    line([x0 x1],[y0 y1],'linewidth',2,'color','b');
    hold on
    plot(x1,y1,'-o','markers',20,'MarkerFaceColor','r');
    grid on
    axis([-1.5 1.5 -1.5 0.5])
    pause(0.01);
    hold off
    K(ct) =getframe(gcf);
    pause(0.9)
    image_name = sprintf('%05d.png',ct);
    saveas(gca,image_name)
    
    ct=ct+1;
end
movie(K)
videofile=VideoWriter('simplependulum_simulation.avi','Uncompressed AVI');
open(videofile)
writeVideo(videofile,K)
close(videofile)

function [dtheta_dt] = ode_func(t,theta,b,g,l,m)
    
    theta1 =theta(1)
    theta2 =theta(2)
    dtheta1_dt =theta2;
    dtheta2_dt = -(b/m)*theta2 - (g/l)*sin(theta1);
    dtheta_dt = [dtheta1_dt;dtheta2_dt];
    
end