Source code for lenstronomy.LensModel.Profiles.numerical_deflections

__author__ = 'dgilman'

from lenstronomy.LensModel.Profiles.base_profile import LensProfileBase

__all__ = ['NumericalAlpha']


[docs]class NumericalAlpha(LensProfileBase): """ This class allows one to incorporate any lens profile into the usage framework of lenstronomy. When creating the instance of LensModel with this lens profile, you must pass in numerical_alpha_class = CustomClass(), where CustomClass is a class with a call method that returns the x/y deflection angles. This allows one to numerically compute and interpolate deflection angles for potentially very complex mass profiles, and then use the results with lenstronomy without having to heavily modify the existing structure of the software. """ def __init__(self, custom_class): """ :param custom_class: a user-defined class that has a __call___ method that returns deflection angles Code example: >>> custom_class = CustomLensingClass() >>> alpha_x, alpha_y = custom_class(x, y, **kwargs) or equivalently: >>> from lenstronomy.LensModel.lens_model import LensModel >>> lens_model_list = ['NumericalAlpha'] >>> lens_model = LensModel(lens_model_list, numerical_alpha_class=custom_class) >>>> alpha_x, alpha_y = lens_model.alpha(x, y, **kwargs) """ self._custom_lens_class = custom_class super(NumericalAlpha, self).__init__()
[docs] def function(self, x, y,center_x = 0, center_y = 0, **kwargs): raise Exception('no potential for this class.')
[docs] def derivatives(self, x, y, center_x=0, center_y=0, **kwargs): """ :param x: x coordinate [arcsec] :param y: x coordinate [arcsec] :param center_x: deflector x center [arcsec] :param center_y: deflector y center [arcsec] :param kwargs: keyword arguments for the custom profile :return: """ x_ = x - center_x y_ = y - center_y f_x, f_y = self._custom_lens_class(x_, y_, **kwargs) return f_x, f_y
[docs] def hessian(self, x, y, center_x=0, center_y=0, **kwargs): """ Returns the components of the hessian matrix :param x: x coordinate [arcsec] :param y: y coordinate [arcsec] :param center_x: the deflector x coordinate :param center_y: the deflector y coordinate :param kwargs: keyword arguments for the profile :return: the derivatives of the deflection angles that make up the hessian matrix """ diff = 1e-6 alpha_ra, alpha_dec = self.derivatives(x, y, center_x=center_x, center_y=center_y, **kwargs) alpha_ra_dx, alpha_dec_dx = self.derivatives(x + diff, y, center_x=center_x, center_y=center_y, **kwargs) alpha_ra_dy, alpha_dec_dy = self.derivatives(x, y + diff, center_x=center_x, center_y=center_y, **kwargs) dalpha_rara = (alpha_ra_dx - alpha_ra) / diff dalpha_radec = (alpha_ra_dy - alpha_ra) / diff dalpha_decra = (alpha_dec_dx - alpha_dec) / diff dalpha_decdec = (alpha_dec_dy - alpha_dec) / diff f_xx = dalpha_rara f_yy = dalpha_decdec f_xy = dalpha_radec f_yx = dalpha_decra return f_xx, f_xy, f_yx, f_yy