You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: quadrotor_dynamics.m
    path of file: ./repos/Robotics-Toolbox/rvctools/release10.3.1/simulink
    
    the code of the file until where you have to start completion: 
function [sys,x0,str,ts] = quadrotor_dynamics(t,x,u,flag, quad, x0, groundflag)
    % Flyer2dynamics lovingly coded by Paul Pounds, first coded 12/4/04
    % A simulation of idealised X-4 Flyer II flight dynamics.
    % version 2.0 2005 modified to be compatible with latest version of Matlab
    % version 3.0 2006 fixed rotation matrix problem
    % version 4.0 4/2/10, fixed rotor flapping rotation matrix bug, mirroring
    % version 5.0 8/8/11, simplified and restructured
   % version 6.0 25/10/13, fixed rotation matrix/inverse wronskian definitions, flapping cross-product bug

    warning off MATLAB:divideByZero
    
    global groundFlag;
        
    % New in version 2:
    %   - Generalised rotor thrust model
    %   - Rotor flapping model
    %   - Frame aerodynamic drag model
    %   - Frame aerodynamic surfaces model
    %   - Internal motor model
    %   - Much coolage
    
    % Version 1.3
    %   - Rigid body dynamic model
    %   - Rotor gyroscopic model
    %   - External motor model
    
    %ARGUMENTS
    %   u       Reference inputs                1x4
    %   tele    Enable telemetry (1 or 0)       1x1
    %   crash   Enable crash detection (1 or 0) 1x1
    %   init    Initial conditions              1x12
    
    %INPUTS
    %   u = [N S E W]
    %   NSEW motor commands                     1x4
    
    %CONTINUOUS STATES
    %   z      Position                         3x1   (x,y,z)
    %   v      Velocity                         3x1   (xd,yd,zd)
    %   n      Attitude                         3x1   (Y,P,R)
    %   o      Angular velocity                 3x1   (wx,wy,wz)
    %   w      Rotor angular velocity           4x1
    %
    % Notes: z-axis downward so altitude is -z(3)
    
    %CONTINUOUS STATE MATRIX MAPPING
    %   x = [z1 z2 z3 n1 n2 n3 z1 z2 z3 o1 o2 o3 w1 w2 w3 w4]
    
    %INITIAL CONDITIONS
    n0 = [0 0 0];               %   n0      Ang. position initial conditions    1x3
    v0 = [0 0 0];               %   v0      Velocity Initial conditions         1x3
    o0 = [0 0 0];               %   o0      Ang. velocity initial conditions    1x3
    init = [x0 n0 v0 o0];       % x0 is the passed initial position 1x3
    groundFlag = groundflag;

    %CONTINUOUS STATE EQUATIONS
    %   z` = v
    %   v` = g*e3 - (1/m)*T*R*e3
    %   I*o` = -o X I*o + G + torq
    
function [sys,x0,str,ts] = quadrotor_dynamics(t,x,u,flag, quad, x0, groundflag)
    % Flyer2dynamics lovingly coded by Paul Pounds, first coded 12/4/04
    % A simulation of idealised X-4 Flyer II flight dynamics.
    % version 2.0 2005 modified to be compatible with latest version of Matlab
    % version 3.0 2006 fixed rotation matrix problem
    % version 4.0 4/2/10, fixed rotor flapping rotation matrix bug, mirroring
    % version 5.0 8/8/11, simplified and restructured
   % version 6.0 25/10/13, fixed rotation matrix/inverse wronskian definitions, flapping cross-product bug

    warning off MATLAB:divideByZero
    
    global groundFlag;
        
    % New in version 2:
    %   - Generalised rotor thrust model
    %   - Rotor flapping model
    %   - Frame aerodynamic drag model
    %   - Frame aerodynamic surfaces model
    %   - Internal motor model
    %   - Much coolage
    
    % Version 1.3
    %   - Rigid body dynamic model
    %   - Rotor gyroscopic model
    %   - External motor model
    
    %ARGUMENTS
    %   u       Reference inputs                1x4
    %   tele    Enable telemetry (1 or 0)       1x1
    %   crash   Enable crash detection (1 or 0) 1x1
    %   init    Initial conditions              1x12
    
    %INPUTS
    %   u = [N S E W]
    %   NSEW motor commands                     1x4
    
    %CONTINUOUS STATES
    %   z      Position                         3x1   (x,y,z)
    %   v      Velocity                         3x1   (xd,yd,zd)
    %   n      Attitude                         3x1   (Y,P,R)
    %   o      Angular velocity                 3x1   (wx,wy,wz)
    %   w      Rotor angular velocity           4x1
    %
    % Notes: z-axis downward so altitude is -z(3)
    
    %CONTINUOUS STATE MATRIX MAPPING
    %   x = [z1 z2 z3 n1 n2 n3 z1 z2 z3 o1 o2 o3 w1 w2 w3 w4]
    
    %INITIAL CONDITIONS
    n0 = [0 0 0];               %   n0      Ang. position initial conditions    1x3
    v0 = [0 0 0];               %   v0      Velocity Initial conditions         1x3
    o0 = [0 0 0];               %   o0      Ang. velocity initial conditions    1x3
    init = [x0 n0 v0 o0];       % x0 is the passed initial position 1x3
    groundFlag = groundflag;

    %CONTINUOUS STATE EQUATIONS
    %   z` = v
    %   v` = g*e3 - (1/m)*T*R*e3
    %   I*o` = -o X I*o + G + torq
    %   R = f(n)
    %   n` = inv(W)*o
    
    % Dispatch the flag.
    %
    switch flag
        case 0
            [sys,x0,str,ts]=mdlInitializeSizes(init, quad); % Initialization
        case 1
            sys = mdlDerivatives(t,x,u, quad); % Calculate derivatives
        case 3
            sys = mdlOutputs(t,x, quad); % Calculate outputs
        case { 2, 4, 9 } % Unused flags
            sys = [];
        otherwise
            error(['Unhandled flag = ',num2str(flag)]); % Error handling
    end