R is one of the most versatile languages for statistical modeling and visualization. It is extensively used in Data Science and Machine Learning as well.
To master this language you should start by practicing the basic concepts of R language which are
1. Basic Syntax
2. Data Structures in R
4. Data Manipulation
5. Data visualization
To get started with these basic concepts here is a comprehensive video that covers most of the topics
You can also check out the following free and end-to-end tutorial to help you decide among your choices
R Programming Tutorial | Learn R Programming | Intellipaat
If you also want a certification along with a course, you can check out the following complete course on Data Science with R.
Learn R Programming Online - R Programming Training Course
This R Programming for Data Science training course will help you be a master in data manipulation with R programming, data visualization and advanced analytics topics like regression and data mining using RStudio. During this course, you will work on real-life projects and assignments to master Data Science.