Sampling a Subset of DataFrame by Group with Sample Size Equal to Another Subset of the DataFrame

Subset Data for a Specific Column with ddply: A Deep Dive in R

Efficiently Merge Data Frames Using R's dplyr Library for Age Group Assignment

Creating Subset of Data Table in R Based on Another Column Condition Using dplyr Library

Writing Per-Variable Counts with Data.tables in R: Efficient CSV File Output Using l_ply Function

Understanding Consecutive Numbering of Data.Frame Segments: A Practical Guide with `plyr` and `dplyr` Libraries