Source code for ctapipe.utils.linalg

from astropy.coordinates import Angle

import numpy as np
from numpy import cos, sin

__all__ = ["rotation_matrix_2d", "length", "normalise", "angle"]

[docs]def rotation_matrix_2d(angle): """construct a 2D rotation matrix as a numpy NDArray that rotates a vector clockwise. Angle should be any object that can be converted into an `astropy.coordinates.Angle` """ psi = Angle(angle).rad return np.array([[cos(psi), -sin(psi)], [sin(psi), cos(psi)]])
[docs]def length(vec): """ returns the length/norm of a numpy array as the square root of the inner product with itself """ return ** 0.5
[docs]def normalise(vec): """ Sets the length of the vector to 1 without changing its direction Parameters ---------- vec : numpy array Returns ------- numpy array with the same direction but length of 1 """ try: return vec / length(vec) except ZeroDivisionError: return vec
[docs]def angle(v1, v2): """ computes the angle between two vectors assuming carthesian coordinates Parameters ---------- v1 : numpy array v2 : numpy array Returns ------- the angle between v1 and v2 as a dimensioned astropy quantity """ norm = np.linalg.norm(v1) * np.linalg.norm(v2) return np.arccos(np.clip( / norm, -1.0, 1.0))