Biomedicine scimago

How are SCImago rankings calculated?
SCImago Journal Rankings
Using Scopus data, SCImago Journal Rank (SJR) offers metrics that are the average number of weighted citations received in year over the number of documents published in the previous three years..
Biomedicines Quartile
The latest Quartile of Biomedicines is Q1.
Each subject category of journals is divided into four quartiles: Q1, Q2, Q3, Q4.
Scopus is an international citation index database for scientific outputs, while SCimago is a database to rank journals and countries/regions based on extracted data from Scopus.
It should be noted that SCimago also includes book series, trade journals, conferences and proceedings.

How are SCImago rankings calculated?