Hello Yan this is Zhaochen He, maintainer of the choroplethr package in R; we previously corresponded by email. I was wondering if could add the choroplethr package to your excellent website; this package has over 300,000+ downloads on CRAN and allows users to go from geographic data to a choropleth map in a single like of code (no downloading shapefiles/geographies needed!).
Link to github/description of package: https://github.com/eastnile/choroplethr