data(USArrests)
| [,1] | Murder | numeric | Murder arrests (per 100,000) |
| [,2] | Assault | numeric | Assault arrests (per 100,000) |
| [,3] | UrbanPop | numeric | Percent urban population |
| [,4] | Rape | numeric | Rape arrests (per 100,000) |
Statistical Abstracts of the United States 1975. (Urban rates).