Input.GetTouch

Hi everyone, I got a simple question how can I make this touch script move in only one direction. For instance I want to move a block by touching my screen and sliding up only, once that happens the block moves only directly up. Heres the script.

 using UnityEngine;
 using System.Collections;
 
 public class TouchFunction : MonoBehaviour {
     public float speed = 0.1F;
     // Use this for initialization
     void Start () {
     
     }
     
     // Update is called once per frame
     void Update () {
         if (Input.touchCount > 0 && Input.GetTouch(0).phase == TouchPhase.Moved) {
             Vector2 touchDeltaPosition = Input.GetTouch(0).deltaPosition;
             transform.Translate(0, touchDeltaPosition.y * speed, 0);
     }
 }
     }