/** {@inheritDoc} */
public double[] gradient(double x, double[] parameters) {
final double a = parameters[0];
final double omega = parameters[1];
final double phi = parameters[2];
final double alpha = omega * x + phi;
final double cosAlpha = FastMath.cos(alpha);
final double sinAlpha = FastMath.sin(alpha);
return new double[] {cosAlpha, -a * x * sinAlpha, -a * sinAlpha};
}
/**
* Simple constructor. Build a vector from its azimuthal coordinates
*
* @param alpha azimuth (α) around Z (0 is +X, π/2 is +Y, π is -X and 3π/2 is -Y)
* @param delta elevation (δ) above (XY) plane, from -π/2 to +π/2
* @see #getAlpha()
* @see #getDelta()
*/
public Vector3D(double alpha, double delta) {
double cosDelta = FastMath.cos(delta);
this.x = FastMath.cos(alpha) * cosDelta;
this.y = FastMath.sin(alpha) * cosDelta;
this.z = FastMath.sin(delta);
}
/** {@inheritDoc} */
public double value(double x, double[] parameters) {
final double a = parameters[0];
final double omega = parameters[1];
final double phi = parameters[2];
return a * FastMath.cos(omega * x + phi);
}