turtlebot not moving for send velocity command

i am running following code on matlab 2017 to run turtlebot2 (ubuntu 14 , ros indigo). iusing followign code i can easily plot laser scan data and my code also displays 'move forward' or move backword' message depending upon the object distance in front of the turtlebot 3d sensor (ros astra pro). and program terminates succefully. but it doe snot moves turtlebot even a single inch. here is my code can any body tell what is worng with it.

IP_OF_HOST_COMPUTER = '192.168.10.13';
ipaddress = 'http://192.168.10.13:11311';
ros_ip = '192.168.10.8';
setenv('ROS_MASTER_URI',ipaddress);
setenv('ROS_IP',ros_ip);
rosinit(ipaddress,'NodeHost',IP_OF_HOST_COMPUTER);
%Create a publisher for the /mobile_base/commands/velocity topic and the corresponding message containing the velocity values.
velpub = rospublisher('/mobile_base/commands/velocity') ;
odom = rossubscriber('/odom');
imsubR = rossubscriber('/camera/rgb/image_raw');
laser = rossubscriber('/scan');
%Wait for the subscriber to return data, then extract the data and assign it to variables x, y, and z:
pause(0.7);
%Receive Scan Data
scan = receive(laser,3);
figure
plot(scan);
    %Create a subscriber for the odometry messages
    odom = rossubscriber('/odom');
    velmsg = rosmessage(velpub)
    odomdata = receive(odom,3);
    pose = odomdata.Pose.Pose;
    %Wait for the subscriber to return data, then extract the data and assign it to variables x, y, and z:
tic;
while toc < 10
  scan = receive(laser,3);
  plot(scan);
end
rostopic info /mobile_base/commands/velocity
%Simple Obstacle Avoidance
spinVelocity = 0.6;       % Angular velocity (rad/s)
forwardVelocity = 0.1;    % Linear velocity (m/s)
backwardVelocity = -0.02; % Linear velocity (reverse) (m/s)
distanceThreshold = 0.3;  % Distance threshold (m) for turning
tic;
  while toc < 5
      % Collect information from laser scan
      scan = receive(laser,2);
      if isempty(scan) 
          disp 'laser data not received or out of sensor range (distance too short or too high)';      
      else
                plot(scan);
                data = readCartesian(scan);      
                  x = data(:,1);
                  y = data(:,2);
                  % Compute distance of the closest obstacle
                  dist = sqrt(x.^2 + y.^2);
                  minDist = min(dist);                    
                  % Command robot action
                  if minDist < distanceThreshold 
                      % If close to obstacle, back up slightly and spin
                      velmsg.Angular.Z = spinVelocity;
                      velmsg.Linear.X = backwardVelocity;
                      disp 'move back';                      
                  else
                      % Continue on forward path
                      velmsg.Linear.X = forwardVelocity;
                      velmsg.Angular.Z = 0;
                      disp 'move forward';                      
                  end   
                    send(velpub,velmsg);
                    pause(0.1);                
      end
  end
rosshutdown

and when i print my variables data using showdetails(velmsg) , i get

velmsg = 
  ROS Twist message with properties:
    MessageType: 'geometry_msgs/Twist'
         Linear: [1×1 Vector3]
        Angular: [1×1 Vector3]
  Linear     
    X :  0.1,     Y :  0,     Z :  0
  Angular    
    X :  0,     Y :  0,     Z :  0