Categories / indexing
Why Pandas' MultiIndex Causes Unexpected Behavior When Removing Unused Levels
Merging on Row Index in R: A Tale of Two Merging Functions - Using Data.table and merge
Adding Index Column to Dataframe Based on Row Values in R
Getting Row Index Based on Multiple Column Values in Pandas Using np.where with df.index
Indexing Foreign Keys in Relational Databases: A Deep Dive