"""
Halo quantity object
"""
#-----------------------------------------------------------------------------
# Copyright (c) 2013-2014, yt Development Team.
#
# Distributed under the terms of the Modified BSD License.
#
# The full license is in the file COPYING.txt, distributed with this software.
#-----------------------------------------------------------------------------
import numpy as np
from yt.utilities.operator_registry import \
OperatorRegistry
from .halo_callbacks import HaloCallback
quantity_registry = OperatorRegistry()
def add_quantity(name, function):
quantity_registry[name] = HaloQuantity(function)
[docs]class HaloQuantity(HaloCallback):
r"""
A HaloQuantity is a function that takes minimally a Halo object,
performs some analysis, and then returns a value that is assigned
to an entry in the Halo.quantities dictionary.
"""
[docs] def __init__(self, function, *args, **kwargs):
HaloCallback.__init__(self, function, args, kwargs)
def __call__(self, halo):
return self.function(halo, *self.args, **self.kwargs)
[docs]def center_of_mass(halo):
if halo.particles is None:
raise RuntimeError("Center of mass requires halo to have particle data.")
return (halo.particles['particle_mass'] *
np.array([halo.particles['particle_position_x'],
halo.particles['particle_position_y'],
halo.particles['particle_position_z']])).sum(axis=1) / \
halo.particles['particle_mass'].sum()
add_quantity('center_of_mass', center_of_mass)
[docs]def bulk_velocity(halo):
if halo.particles is None:
raise RuntimeError("Bulk velocity requires halo to have particle data.")
return (halo.particles['particle_mass'] *
np.array([halo.particles['particle_velocity_x'],
halo.particles['particle_velocity_y'],
halo.particles['particle_velocity_z']])).sum(axis=1) / \
halo.particles['particle_mass'].sum()
add_quantity('bulk_velocity', bulk_velocity)