MATLAB serial communication problem.Urgent help needed

Hi all.
this is my first post in this forum,and I urgently need your help.

I have to make a robot car that can grab an object based on its color.The image processing is done on matlab,and based on the position,it sends data to arduino(I am using arduino uno R3).The matlab code looks like this:

%%%image acquisition codes

pause on;

%send_command = 'S' Stall
%               'F' Go forward
%               'R' Go Right
%               'L' Go left
%               'B' Go Backward
%               'O' Open Gripper
%               'C' Close Gripper

I urgently need your help.

Your homework is do when?

Sorry,somehow this got posted.The link of the topic is this

Try Serial.print(in_inbyte); rather than Serial.write

Same result.