Julia for Data Analysis

11 Converting and grouping data frames

This chapter covers

• Converting data frames to other Julia types
• Writing type-stable code
• Understanding type piracy
• Grouping data frame objects
• Working with grouped data frames

In chapter 10, we reviewed various ways that DataFrame objects can be constructed from different data sources. In this chapter, we discuss the reverse process and show how you can create other objects from a data frame (recall from chapter 9 that a data frame can be a DataFrame or its view, that is, a SubDataFrame). You might want to perform such an operation in two scenarios.

In the first scenario, you need to perform analytical tasks provided by functions that do not accept a data frame as input, but instead accept another type, ...