Question

Sorry in advance, I’m struggling a bit with how to explain this… 🙂

Essentially, I’ve got a typical windows coordinate system (the Top, Left is 0,0). If anybody’s familiar with the haversine query, like in SQL, it can get all points in a radius based on latitude and longitude coordinates.

I need something much simpler, but my math skills ain’t all up to par! Basically, I’ve got random points scattered throughout about a 600×400 space. I have a need to, for any X,Y point on the map, run a query to determine how many other points are within a given radius of that one.

If that’s not descriptive enough, just let me know!

Answer 1

Use Pythagoras:

distance = sqrt(xDifference^2 + yDifference^2) 

Note that ‘^’ in this example means ‘to the power of’ and not C’s bitwise XOR operator. In other words the idea is to square both differences.