Here's a summary of the provided information and some additional examples to demonstrate the usage of the `melt()` function in R:

Unstacking Data with Pandas in Python: A Step-by-Step Guide

Advanced Grouping and Reshaping Transformation Using Pandas

Pivot Pandas DataFrame Column Values for Data Reformatting

Reshaping Data in R: The Power of Two Value Variables in Cast Function

Melting a Pandas DataFrame from Wide to Long Format Twice on the Same Column