In this chapter, we will cover the following topics:

• Tidying variable values as column names with stack
• Tidying variable values as column names with melt
• Stacking multiple groups of variables simultaneously
• Inverting stacked data
• Unstacking after a groupby aggregation
• Replicating pivot_table with a groupby aggregation
• Renaming axis levels for easy reshaping
• Tidying when multiple variables are stored as column names
• Tidying when multiple variables are stored as column values
• Tidying when two or more values are stored in the same cell
• Tidying when variables are stored in column names and values
• Tidying when multiple observational units are stored in the same table