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.
The complement of a set A (denoted by Aâ) is the set of elements which are not in set A. Hence, A' = {x | x â A}. More specifically, A'= (U â A) where U is a universal set which contains all objects. Cartesian Product / Cross Product. The Cartesian product of n number of sets A1, A2 .....An, defined as A1 Ã A2 Ã.....