R's data.table package extends data.frame:

A general-purpose tool for dynamic report generation in R

Create Blogs and Websites with R Markdown

Easily install and load packages from the tidyverse

caret (Classification And Regression Training) R package that contains misc functions for training and plotting classification and regression models

Improve the readability of R code with the pipe

Encapsulated object-oriented programming for R

Source code for Kabacoff, R. R in Action (3rd edition). Manning: Boca Raton, FL.