Send values in a variable from Matlab to arduino using serial communications

Dear all, may I know how to send a values (numbers) in a variables from MATLAB to ARDUINO.

Below is my coding but error arise.

                        %Compute Standard Deviation of x and send it to serial
                        sdA = std(x) 
                        s = serial('COM6');
                       s.Baudrate = 9600;
                        s.Terminator = 'CR';
                        %open serial port
                        fopen(s);
                        %send value '100' else send 101
                        fprintf(s,'sdA');
                         fscanf(s);
                         fclose(s);