Tapply
shape
merge() function, which combines two data frames by common columns or row names, similar to SQL joins. You can control how the data frames are merged (e.g., inner, outer, left, or right join) by specifying different options. ggplot2 is a popular data visualization package in R that provides a powerful and flexible framework for creating a wide range of static graphics. It is based on the Grammar of Graphics (hence the gg), which provides a systematic approach to building visualizations by layering different components.