Java atan2 atan2(double y, double x)

Description

atan

License

Open Source License

Declaration

public static final double atan2(double y, double x) 

Method Source Code

//package com.java2s;

public class Main {
    public static final double atan2(double y, double x) {
        double atn = atan(y / x);

        if (y >= 0) {
            if (x >= 0)
                return atn;
            return Math.PI + atn;
        }//from w  w w .  j av a  2  s.  c  om
        if (x >= 0) {
            return atn;
        }
        return -Math.PI + atn;
    }

    /** returns [-PI/2, PI/2]
    accurate within 0.014 degrees
     **/
    public static final double atan(double x) {
        if (Math.abs(x) <= 1)
            return atan_mag1(x);
        if (x < 0)
            return -Math.PI / 2 - atan_mag1(1 / x);
        else
            return Math.PI / 2 - atan_mag1(1 / x);
    }

    protected static final double atan_mag1(double x) {
        // accuracy = 0.26814 degrees
        //   return x/(1+0.28087207802773*x*x);

        if (true) {
            if (Math.abs(x) > 1)
                System.out.printf("ATAN_MAG1: %15f\n", x);

            final double p0 = -0.000158023363661;
            final double p1 = 1.003839939589617;
            final double p2 = -0.016224975245612;
            final double p3 = -0.343317496147292;
            final double p4 = 0.141501628812858;

            double a = Math.abs(x);
            double a2 = a * a;

            double y = p0 + p1 * a + p2 * a2 + p3 * (a2 * a) + p4 * (a2 * a2);

            if (x < 0)
                return -y;
            return y;
        } else {
            double xx = x * x;

            // accuracy = 0.10550 degrees (according to matlab)
            return (0.00182789418543 + 0.97687229491851 * x + 0.00087659977713 * xx)
                    / (0.99499024627366 + 0.00228262896304 * x + 0.25288677429562 * xx);
        }
    }
}

Related

1. atan2(double arg1, double arg2)
2. atan2(double x, double y)
3. atan2(double y, double x)
4. atan2(double y, double x)
5. atan2(double y, double x)
6. atan2(double[] arr1, double[] arr2)