If you have a vector of coordinate for a set of points, you might want to differentiate those points. To do that a concept called logical indexing will help you pull out a subset of those points easily.
Here is a quick example (See the second video for more details)
>> L = logical([0 1 0 1])
0 1 0 1
>> a = [1 2 3 4]
1 2 3 4
The above video made practical use of logical indexing. The video below shows logical indexing in a more academic treatment.