Can someone please help me out with this MATLAB code. It is giving error "INDEX EXCEEDS THE NUMBER OF ARRAYS_ INDEX MUST NOT EXCEED 1" ON LINE 69

clear ALL
 m11 = int8 ( zeros (100) )
 % T1t(i) = int8 ( Zeros (100))
 % T2t(i) =  int8( Zeros (100))
 m1 = 1 ;
 m2 = 2;
 l1 = 1;
 l2 = 1.2;
 I1 = 0.12;
 I2 = 0.25 ;
 me = 2 ;
 Ic1 = 0.25 ;
 Ic2 = 0.6 ;
 v1 = 5.5 ;
 v2 = 2.7 ;
 k1 = 2 ;
 k2 = 1 ;
 g = 9.8 ;
    dt= 0.01
     % t = 0 ;
   Points = 30000
    Data = zeros(Points,4);
 D = [ 100 ; 50];
 F = [ 30 ; 30 ]
   theta1t(1) =  1 ;
   theta2t(1) = 0.01 ;
   thetav1t(1) = 0;
   thetav2t(1) = 0 ;
   thetaa1t((1)) = 0 ;
   thetaa2t((1)) = 0 ;
   
      
 
for   i = 1 : 1000
      
       t(i) = i
       t(i+1) = (i+1)* dt
      
     
                     
    qd1  =   pi/6*(1-cos(2*pi*t(i))+1.5*sin(.5*pi*t(i)))

    qd2 =  pi/4*(1-cos(2*pi*t(i))+2.5*sin(.75*pi*t(i)))

    qdv1 = (pi^2)/3*sin(2*pi*t(i))+(pi/6)*(1.5*0.5*pi)*cos(.5*pi*t(i))

  qdv2 = (pi^2)/2*sin(2*pi*t(i))+(pi/4)*(2.5*0.75*pi)*cos(.75*pi*t(i))
  
  qda1 = 2*(pi^3)/3*cos(2*pi*t(i))-(pi/6)*(1.5*0.5*pi)*(0.5*pi)*sin(.5*pi*t(i)) 

  qda2  = (pi^3)*cos(2*pi*t(i))-(pi/4)*(2.5*0.75*pi)*(0.75*pi)*sin(.75*pi*t(i))

  m11 =  ((l2*l2*m2)/(2*l1*l2*m2*cos(theta2t(i))))+( l1*l1*(m1-m2))
  m12 = ( l2*l2*m2)  + ( l1*l2*m2*cos(theta2t(i)))
  m21 = (( l2*l2*m2 )/(l1*l2*m2*cos(theta2t(i))))
  m22 = ( l2*l2*m2 )
  m = [ m11 , m12 ; m21 ,m22]
  v11 = (-m2*l1*l2*sin(theta2t(i))*(thetav2t(i))*(thetav2t(i))) -( 2*m2*l1*l2*sin(theta2t(i))*(thetav1t(i))*(thetav2t(i)))
  v21 = m2*l1*l2*sin(theta2t(i))*(thetav1t(i))*(thetav1t(i))
  V = [v11;v21 ]
  G11= (m2*l2*g*cos(theta1t(i)+theta2t(i))) + (( m1+m2)*l1*cos(theta1t(i)))
  G21 = m2*l2*g*cos(theta1t(i) + theta2t(i))
  G  = [G11; G21]  
  T1(i) = m2*l2*l2*(thetaa1t(i)+thetaa2t(i)) + (m2*l1*l2*cos(theta2t(i))*(2*thetaa1t(i)) + thetaa2t(i)) + ((m1+m2)*l1*l1*thetaa1t(i)) - (m2*l1*l2*(sin(theta2t(i)))*thetav2t(i)*thetav2t(i)) - ( 2*m2*l1*l2*(sin(theta2t(i)))*thetav1t(i)*thetav2t(i))+(m2*l2*g*sin(theta1t(i)+theta2t(i))) + ((m1+m2)*l1*g*sin(theta1t(i)))+(v1*thetav1t(i))+(k1*sin(thetav1t(i)))
  T2(i) = (m2*l1*l2*cos(theta2t(i))*thetaa1t(i)) +(m2*l1*l2*sin(theta2t(i))*thetav1t(i)*thetav1t(i)) + (m2*l2*g*sin(theta1t(i)+theta2t(i)))+(m2*l2*l2*(thetaa1t(i)+thetaa2t(i)))+(v2*thetav2t(i))+(k2*sin(thetav2t(i)))
   T = [ T1(i) ;T2(i)]
   n = inv(m)
   thetaa   =  n*[T -V - G -F -D]
   thetaa1t(i)  =   thetaa(1,1)
   thetaa2t(i)   =   thetaa(2,1)
     
   thetav1t(i+1) =  thetav1t(i) +thetaa1t(i)*dt
   thetav2t(i+1) =  thetav2t(i)+ thetaa2t(i)*dt
          
   theta1t(i+1) = theta1t(i) + thetav1t(i)*dt +( 1/2)*thetaa1t(i)*dt*dt
   theta2t(i+1) = theta2t(i) + thetav2t(i)*dt + (1/2)*thetaa2t(i)*dt*dt

    % Errors 
    e1t(i) = abs(theta1t(i)-qd1)
    e2t(i) = abs(theta2t(i) - qd2)
    ed1t(i) = abs(thetav1t(i)- qdv1)
    ed2t(i) = abs(thetav2t(i)-qdv2)    

end 

ax = gca ;
ax.XAxislocation = "origin";
ax.YAxislocation ="origin";
xlabel ( 'time');
ylabel ('Torque1') ;
Legend ('T1','T2')
Plot ( t , T1,'r')
hold on
Plot (t,T2 ,'b')
hold off


 

Answer 1

[DGM]

thetaa1t and thetaa2t are initialized as scalars

thetaa1t((1)) = 0 ;
thetaa2t((1)) = 0 ;

I imagine you're trying to grow them, but when you make the assignments here, you're only assigning to the current index instead of i+1, so they never grow.

thetaa1t(i)  =   thetaa(1,1)
thetaa2t(i)  =   thetaa(2,1)

... that's probably why.