Getting the difference between two headings

If I understand the question correctly, I think the following code should work:

private double GetHeadingError(double initial, double final)
{
            if(initial == 360) initial = 0;
            if(final == 360) final = 0;
            double clockWise = (final - initial);
            double counterClockWise = (360 - final + initial);
            return (Math.Abs(clockWise) <= Math.Abs(counterClockWise)) ? clockWise : -counterClockWise;
}

Basically I'm treating 360 degrees the same as 0, which I believe is ok. This code will produce the same results as listed in the table above. Code does not do bounds checking, it is expecting values between 0 and 360.

Edit: added check for when the difference is exactly 180 degrees. previously this was returning either 180 or -180 depending on whether final was greater or lower than initial. I've modified it so that it returns positive 180 in both cases.

---

So here's my attempt...

private static double GetHeadingError(double initial, double final)
        {
            if (initial > 360 || initial < 0 || final > 360 || final < 0)
            {
                //throw some error
            }

            var diff = final - initial;
            var absDiff = Math.Abs(diff);

            if (absDiff <= 180)
            {
                //Edit 1:27pm
                return absDiff == 180 ? absDiff : diff;
            }

            else if (final > initial)
            {
                return absDiff - 360;
            }

            else
            {
                return 360 - absDiff;
            }
        }

Here's a straightforward solution, albeit named a bit differently and in Dart. Based on this avionics answer.

/// The difference of two headings in degrees such that it is always in the range
/// (-180, 180]. A negative number indicates [h2] is to the left of [h1].
double headingDiff(double h1, double h2) {
  double left = h1 - h2;
  double right = h2 - h1;
  if (left < 0) left += 360;
  if (right < 0) right += 360;
  return left < right ? -left : right;
}

Edit: There's an even more concise answer here, but I haven't tried it myself:

double headingDiff(double h1, double h2) => (h2 - h1 + 540) % 360 - 180;