How can ı rotate FPS camera with touch?

I have a simple FPS CONTROLLER from the standard assets . My game is for andriod platform i want to the convert the camera rotation through swipe or joystick or touch etc but i want it to do through the code not the standard assets joysticks..... i'm able to move the player through the code but unable to implement the FPS CAMERA rotation through touch..... if anyone can help i'll be very thankful