Interesting! Up until now, we've worked with basic variables and vectors. This time, though, notice that the cities variable contains tabular data. Perhaps you are more familiar with the term "spreadsheet" that is used in Excel or the term "database table" that is used in database languages. In R, a "table" is simply called a data frame!
A data frame is a collection of vectors arranged as columns that each have their own names. For instance, the cities data frame contains five column vectors: country, city, latitude, longitude, and population. The vectors country and city are character vectors; latitude, longitude, and population are numeric vectors.
We'll refer to these vectors of a data frame as just columns. You can think of a data frame as a two-dimensional array – each entry in a data frame is related to one specific column and one specific row.
| cities | COLUMN | |||||
|---|---|---|---|---|---|---|
| id | country | city | latitude | longitude | population | |
| 1 | France | Paris | 48.866693 | 2.33333533 | 4957588.5 | |
| 2 | Germany | Berlin | 52.521819 | 13.40154862 | 32500.4.0 | |
| 3 | Germany | Frankfurt | 50.099977 | 8.67501542 | 1787332.0 | |
| 4 | Germany | Stuttgart | 48.779980 | 9.19999630 | 1775644.0 | ROW |
| 5 | Germany | Hamburg | 53.550025 | 9.99999914 | 1748058.5 | |
| 6 | Poland | Warsaw | 52.250001 | 20.99999955 | 1704569.5 | |
| 7 | Portugal | Lisbon | 38.722723 | -9.14486631 | 1664901.0 | |
| 8 | Poland | Katowice | 50.260380 | 19.0200.405 | 1527362.0 | |
We've set up a data frame named countries.
Display the information stored in this data frame, and observe the data that are returned. Notice that this data frame only contains countries from Western and Eastern Europe.
Just type
countries
in the editor.
