All the elements of the main diagonal of the original relation R matrix are converted into 1.

Supplement:

In discrete mathematics, for the relationship that is neither reflexive nor anti-reflexive, we should add some order pairs appropriately to make it reflexive, and at the same time, we should add as few order pairs as possible. The relation after adding the ordered pair is called the reflexive closure of the original relation, and it is recorded as r(R).

Example:

Let A={ 1, 2,3} and r = {

Solution: Because R lacks ordered pairs.

From the process of finding reflexive closure, we can get: r(R)=RUIA.