Camera.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Camera : MonoBehaviour
{

  public GameObject graph;
  public float speed = 5.0f;
  
    void Start(){}

    void Update()
    {
      // find centre of the graph
      float minx = 1000000.0f; float maxx = 0.0f;
      float miny = 1000000.0f; float maxy = 0.0f;
      float minz = 1000000.0f; float maxz = 0.0f;      
      foreach (Transform child in graph.transform){
	if (child.position.x < minx) minx = child.position.x;
	if (child.position.x > maxx) maxx = child.position.x;
	if (child.position.y < miny) miny = child.position.y;
	if (child.position.y > maxy) maxy = child.position.y;
	if (child.position.z < minz) minz = child.position.z;
	if (child.position.z > maxz) maxz = child.position.z;			
      }
      transform.LookAt(new Vector3((minx+maxx)/2,(miny+maxy)/2,(minz+maxz)/2));
      if (Input.GetKey("up")){
	transform.position += new Vector3(0,0,Time.deltaTime*speed);
      }
      if (Input.GetKey("down")){
	transform.position -= new Vector3(0,0,Time.deltaTime*speed);
      }      
    }
    
}