Question

Firstly, this may sound very trivial, but currently I am creating a function getQuadrant(degree) for returning a quadrant from a given angle.

For instance, if degree is >= 0 and < 90, it will return 1. If degree is >= 90 and < 180, it will return 2. And so forth. This is very trivial. However, to be able to deal with degrees other than 0-360, I simply normalized those numbers to be in 0-360 degree range first, like this:

            while (angle > 360)
                angle = angle - 360;
            end

            while (angle < 0)
                angle = angle + 360;
            end

After that, I calculate. But to be frank, I hate using while statements like this. Are there other mathematical ways that can point out the quadrant of the angle in one go?

EDIT: I see that there are lots of good answers. Allow me to add “which algorithm will be the fastest?“

Answer 1

Take advantage of integer arithmetics:

angle = angle - (angle/360)*360;
if (angle < 0) angle = angle + 360;

The idea is, since angle/360 is rounded down (floor()), (angle/360) gives you the k you need to do alpha = beta + 360k.

The second line is normalizing from [-359,-1] back to [1,359] if needed.