While editing the maps, you may notice that some of the roads are not labeled properly. This means, the road type might be wrong (a highway is marked as a street) or that one road has a few road types (a highway is marked as Freeway, highway and primary at different segments). The importance of proper labeling is in two aspects:
Other sites. R 101: The Subset Function. The subset function is available in base R and can be used to return subsets of a vector, martix, or data frame which meet a particular condition. In my three years of using R, I have repeatedly used the subset() function and believe that it is the most useful tool for selecting elements of a data structure.
Mathematics. 1  a mode of separating a positive whole number into a sum of positive whole numbers. 2  the decomposition of a set into disjoint subsets whose union is the original set: A partition of the set (1, 2, 3, 4, 5) is the collection of subsets (1), (2, 3), (4), and (5).