I have a sample of 1000 data points and I used it as the training sample to forecast with Timeseries. My lecture suggested me comparing the ACF with its critical values (upper and lower) numerically rather than looking at the graph. 

Here are my ACF values: 

[![enter image description here][1]][1]

**Question:** How do I come up with the upper and the lower critical values for the ACF? Is there any function in R to yield these values? 


  [1]: https://i.sstatic.net/RJiYb.png