01 Mar 2015 by Andy

Mean Angle

Description

Arithmetic mean may not always be suited for circular quantities like angles, day times, fractional quantities. e.g Mean angle of 0 degrees & 360 degrees arithmetically is 180. However, 0 degrees & 360 degrees are the same value and the mean should be zero.

Input

An IEnumerable<double> expecting angle values in radians

Output

The mean angle in radians

Contract

IMathUtilities

double MeanAngle(IEnumerable<double> angleValues);

Test Cases

MeanAngleof0and360_ShouldBeZero

Created By Super Human

public void MeanAngleof0and360_ShouldBeZero(IMathUtilities m) { double tolerance = 0.0000000001; Assert.AreEqual(0, m.MeanAngle(new double[] { 0, 2*Math.PI }), tolerance); }

MeanAngleOfMoreThanTwoAngles_ShouldReturnCorrectValue

Created By Super Human

public void MeanAngleOfMoreThanTwoAngles_ShouldReturnCorrectValue(IMathUtilities m) { double tolerance = 0.0000000001; Assert.AreEqual(-Math.PI/2, m.MeanAngle(new double[] { Math.PI / 2, Math.PI, (3d/2d) * Math.PI, 2 * Math.PI}), tolerance); }

MeanAngleofSingleAngleShouldReturnSame

Created By K Bonneau

public void MeanAngleofSingleAngleShouldReturnSame(IMathUtilities m) { double tolerance = 0.0000000001; Assert.AreEqual(Math.PI, m.MeanAngle(new double[] { Math.PI }), tolerance); }

You must be logged in to add test cases

2 Solutions

01 Mar 2015 by Andy

For circular mean, we need to find both the x & y components for each angle (assuming they are part of the unit circle). i.e. x component would be the Cosine of the angle, and y component is the Sine of the angle. Find the mean separately for both the components, and then do the reverse, i.e find the angle from these mean components using arc tangent function.

public class Solution : IMathUtilities { public double MeanAngle(IEnumerable<double> angleValues) { double xValue = 0, yValue = 0; int numValues = 0; foreach(var angle in angleValues) { xValue += Math.Cos(angle); yValue += Math.Sin(angle); numValues++; } return Math.Atan2 (yValue / numValues, xValue / numValues); } }

Test Case Run Summary

MeanAngleof0and360_ShouldBeZero

MeanAngleOfMoreThanTwoAngles_ShouldReturnCorrectValue

MeanAngleofSingleAngleShouldReturnSame

download solution

Try this Solution

Comments

31 Mar 2015 by bobloki

Turned it into a one liner linq statement.

public class Solution : IMathUtilities { public double MeanAngle(IEnumerable<double> angleValues) { return Math.Atan2(angleValues.Sum(i => Math.Sin(i)) / angleValues.Count(), angleValues.Sum(i => Math.Cos(i)) / angleValues.Count()); } }

Test Case Run Summary

MeanAngleof0and360_ShouldBeZero

MeanAngleOfMoreThanTwoAngles_ShouldReturnCorrectValue

MeanAngleofSingleAngleShouldReturnSame

download solution

Try this Solution

Comments

Add Solution