Week 3 - Solving second order ODEs

https://youtu.be/Ra1_oplG1lk

%defining ode function for simple pendulum.

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/t)*sin(theta1);
         dtheta_dt = [dtheta1_dt;dtheta2_dt];
end

% second order ode simple pendulum

close all
clear all
clc


%step1 : inputs

%damping co_eff
b = 0.05;

%gravity
g = 9.81;

%length of string
l = 1;

%mass 
m = 0.1;

%step2 : initial condition
theta_0 = [0;5];

%step3 : time points
t_span = linspace(0,10,5000;

%step4 : solving ode function
[t , results] = ode45(@(t,theta)ode_func(t,theta,b,g,l,m),t_span,theta_0);

%step5 : plotting
plot(t,results(:,1))
hold on
plot(t,results(:,2))
xlabel(time)
ylabel(plot)

%Step6 : animating pendulum
amplitude = results(:,1)
p = 1;

for i = length(amplitude);
    angle = amplitude(i);
    figure(1)
    tite('simple pendulum')
    
    x0 = 0;
    y0 = 0;
    
    x1 = l*sin(angel);
    y1 = -l*cos(angle);
    
    plot([-1. 1.1],[0 0],'linewidth',2);
    hold on 
    plot([x0 x1],[y0 y1],'linewidth',2);
    plot(x1,y1,'o','MarkerSize',20,'MarkerFaceColor','b');
    hold off
    axis([-1.5 1.5 -1.5 0.5]);
    pause(0.003);
    M(p) = getframe(gcf);
    p = p+1;
end

%Step7 creating video file
movie(M)
videfile = VideoWriter('simple_pendulum.avi','uncompressed avi')
open('videofile')
writeVideo('vifeofile,M)
close('videofile')



 

the following error was found and rectified with the help of mentor provided by skill-link.