Index exceeds the number of array elements. Index must not exceed 1.

% find the damping coefficient using the plot below (use the figure to do trial and error):
c_num = 500 ;

% define the time interval and the number of integration steps
n    = 10000; 
t    = zeros(n,1);
tf   = 5;
t(1) = 0;
delt = (tf-t(1))/n;

% initializing variables
x    = zeros(n,1);
v    = zeros(n,1);

m = 12 ; % kg
k = 10000 ; % N/m
J = 0.016 ; % kg m^2
r = 0.340 ; % m 


% assign initial conditions (be careful of the units)
x(1) =      0.03 ; % m 
v(1) =  -0.2 ; % m/s


% start the integration directly from the second step (with i=2)
for i=2:1:n


    % update the velocity and acceleration for x at step i 
    
    dx_ = v(i-1) ;
    ddx_ = -(c_num*dx_(i-1) + k*x(i-1))/(m + J/r^2);
    

    % integrate x and v
    x(i) = x(i-1) + dx_*delt ; 
    v(i) = v(i-1) + (-c_num/m*v(i-1) - k/m*x(i-1))*delt ; 
    
    % integrate time
    t(i) = t(i-1) + delt ;
    
end % end of each integration step  

Index exceeds the number of array elements. Index must not exceed 1.

Please advise on the index error.

[James Tursa]

+1 for including units in comments

Answer 1

[Walter Roberson]

    dx_ = v(i-1) ;

dx_ will be a scalar

    ddx_ = -(c_num*dx_(i-1) + k*x(i-1))/(m + J/r^2);

But you index it there.