How to count average value for each user?

I have two tables: users, comments.

Each user has some comments.

I do request like as:

$users = User:with('comments')->get();

How can I count the average value in field comments.rate where users.id = comments.user_id

In result I should get collection with all rows wityh user information and field avg_rate

I tried to use ->avg(), but it returns only one row, not for each

via Chebli Mohamed