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Introduction
The lapply() function
Other apply() functions
The split-apply-combine pattern
Summary
22. Summary

## Instruction

Excellent work! You learned quite a lot about the apply family of functions in this section. Let's briefly review what we learned.

Special apply() functions can be used when you want to perform certain calculations on each member of a list. The three functions we looked at are:

• lapply() – takes a list or vector as its first argument and the name of the function to apply as the second. Returns a list.
• sapply() – takes a list or vector as its first argument and the name of the function to apply as the second. Simplifies the output by returning a vector or data frame.
• tapply() – takes a vector of data, a vector of labels, and a function to apply. Groups the data according to the label using the function provided.

Let's review what we learned with some exercises!

## Exercise

Click to continue.