How can I replace a mousePosition for a touchPosition, updating in every frame?

Hi, I have that script for a player in the center of the screen in a 2d game to he rotate turning his forward to the mousePosition, I want to do the same thing, but with the touch to the player turning his forward to where the finger is touching, I tried a lot of things, but I can´t do his rotate in every touch or sliding, please help me!

#pragma strict

function Start () { 
	Screen.showCursor = false;
}

function Update () {
	var playerPlane = new Plane (Vector3.up,transform.position);
	var ray = Camera.main.ScreenPointToRay (Input.mousePosition);
	var hitdist = 0.0;
	
	if (playerPlane.Raycast (ray,hitdist)) {
		var targetPoint = ray.GetPoint(hitdist);
		var targetRotation = Quaternion.LookRotation(targetPoint - transform.position);
		transform.rotation = targetRotation;
	}
}

I resolve, my error before are using Time.deltaTime, I don’t know why that works now:

#pragma strict

var speed:float = 20.0;

function Start () { 
	Screen.showCursor = false;
}

function Update () {
	if (Input.touchCount > 0) {
		var touchPos:Vector2 = Input.GetTouch(0).position;
		var touchPos3:Vector3 = Vector3(touchPos.x*speed,touchPos.y*speed,0);
		var playerPlane = new Plane (Vector3.up,transform.position);
		var ray = Camera.main.ScreenPointToRay (touchPos3);
		var hitdist = 0.0;
	
		if (playerPlane.Raycast (ray,hitdist)) {
			var targetPoint = ray.GetPoint(hitdist);
			var targetRotation = Quaternion.LookRotation(targetPoint - transform.position);
			transform.rotation = targetRotation;
		}
	}
}