Cannot plot time vs displacement graph

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Gazza Dazzle 2014-9-5

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关闭： Steve Miller 2022-12-21

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Hi I am struggling to plot time vs displacement graph for my pendulum program, i can only plot the animation of the pendulum but not a graph of it. Any ideas?

thanks

l=0.4;
m=0.5;
g=9.81;
b=0.05;
sampling=0.01;
runningstep=200;
timespan=sampling*runningstep;
x0=[pi/4
    0];
%main program for numberical solution
k=1;
while(k<1000)
    [t,y]=ode45(@pendulum,[0 sampling],x0,[],l,b,m); 
    if k==1
        yp(1,:)=y(1,1:2);
        tp(1,:)=t(1,1);
    else
        yp(k,:)=y(size(y,1),1:2);
        tp(k,1)=sampling*k;
    end
    %update date
    x0=y(size(y,1),1:2); %change initial value
    k=k+1;
end
%Time Displacement Graph
plot(t,y)
title('time displacement graph')
%animation
xa=l*sin(yp(:,1));
ya=-l*cos(yp(:,1));
hp=plot([0,0],[xa(1),ya(1)],'linewidth',2,'Marker','o','Erasemode','xor');
axis([-l-0.1 l+0.1 -l-0.1 l+0.1]);
title('Pendulum problem');
xlabel('Displacement (degrees)');
ylabel('Angular velocity (radians/sec.)');
for i=1:size(tp)
   set(hp,'xdata',[0,xa(i)],'ydata',[0,ya(i)]);
   drawnow
   pause(0.01);
   grid on
   mov(i)=getframe;
end
movie2avi(mov,'pendulum.avi')
funtion file
function dy=pendulum(t,y,l,m,b)
dy(1,1)=y(2,1);
dy(2,1)=-9.81/l*sin(y(1,1)-b/(m*l^2)*y(2,1));