Introduction to data frames
Data frame structure
Accessing columns in a data frame
9. Accessing columns with $
Accessing rows of a data frame
Accessing rows and columns combined in a data frame
Data frame analysis


Great job! Another popular method of accessing a single column of a data frame involves using the dollar sign ($) operator, like this:


Basically, after you specify the data frame name, you simply type the $ sign followed by the name of the column you wish to retrieve.

In our case here with cities$city, we simply retrieve the city column from the cities data frame. Mind that the result is not the same as what you'd get with cities["city"]. The $ notation returns a vector. The brackets notation returns a data frame.


Display the values of the column named country from the countries data frame. Use the dollar sign ($) operator.