This chapter looked at the common problems in large, messy datasets common in machine learning projects. These include, but are not limited to the following:

• Missing or invalid values
• Novel levels in a categorical feature that show up in algorithm production
• High cardinality in categorical features such as zip code
• High dimensionality
• Duplicate observations

This chapter provided a disciplined approach to dealing with these problems by showing how to explore the data, treat it, and create a dataframe that you can use for developing your learning algorithm. It's also flexible enough that you can modify the code to suit your circumstances. This methodology should make what many feels is the most arduous, time-consuming, and least enjoyable part of the job an easy task.

With this task behind us, we can now get started on our first modeling task using linear regression in the following chapter.