Split it

Often, you will have data for multiple groups together in one data frame. The cash data frame was an example of this back in Chapter 3. There were cash_flow and year columns for two groups (companies A and B). What if you wanted to split up this data frame into two separate data frames divided by company? In the next exercise, you will explore why you might want to do this, but first let's explore how to make this happen using the split() function.

Create a grouping to split on, and use split() to create a list of two data frames.

grouping <- cash$company
split_cash <- split(cash, grouping)

split_cash 

$A
  company cash_flow year
1       A      1000    1
2       A      4000    3
3       A       550    4

$B
  company cash_flow year
4       B      1500    1
5       B      1100    2
6       B       750    4
7       B      6000    5

To get your original data frame back, use unsplit(split_cash, grouping).

The cash data frame is available in your workspace.
Create a new grouping from the year column.
Use split() to split cash into a list of 5 data frames separated by year. Assign this to split_cash.
Print split_cash.
Use unsplit() to combine the data frames again. Assign this to original_cash.
Print original_cash to compare to the first cash data frame.

Exercise

Split it

Instructions