Simplifying list-columns

1. Why might the lengths() function be useful for creating atomic vector columns from list-columns?

The lengths() function returns the lengths of each element in a list. It could be useful for testing whether all elements in a list-column are the same length. You could get the maximum length to determine how many atomic vector columns to create. It is also a replacement for something like map_int(x, length) or sapply(x, length).

2. List the most common types of vector found in a data frame. What makes lists different?

The common types of vectors in data frames are:

• logical
• numeric
• integer
• character
• factor

All of the common types of vectors in data frames are atomic. Lists are not atomic since they can contain other lists and other vectors.