This package is available from CRAN (Comprehensive R Archive Network).

Link to CRAN

The Comprehensive R Archive Network (CRAN) contains the source code for many packages that have been contributed to the R Project. There are many CRAN mirror sites.

1. Connect to the List of CRAN Mirror Sites.

2. Select the closest site.

3. Under the section Source Code for all Platforms select Source Code of Contributed Packages

4. Find the required package.

5. Download the appropriate file for your operating system.