simple example code: clump_finding.pyΒΆ

(Source code, png, hires.png, pdf)

../../_images/clump_finding.png
"""
Generates a random distribution of particles and uses Hop to determine clumps
in the particle set.
"""
from __future__ import print_function

import numpy
from numpy import random
from matplotlib import pyplot

from amuse.units import units
from amuse.units import nbody_system
from amuse.community.hop.interface import Hop

from amuse.datamodel.particles import Particles
from amuse.ic.salpeter import new_salpeter_mass_distribution

def new_cluster(number_of_stars = 1000):
    masses = new_salpeter_mass_distribution(
        number_of_stars,
        mass_min = 0.1 | units.MSun,
        mass_max = 125.0 | units.MSun,
        alpha = -2.35
    )

    particles = Particles(number_of_stars)
    particles.mass = masses
    particles.x = units.parsec(random.gamma(2.0, 1.0, number_of_stars))
    particles.y = units.parsec(random.gamma(1.0, 1.0, number_of_stars))
    particles.z = units.parsec(random.random(number_of_stars))

    return particles


def find_clumps(particles, unit_converter):

    hop = Hop(unit_converter)
    hop.particles.add_particles(particles)
    hop.calculate_densities()
    hop.do_hop()

    result = [x.get_intersecting_subset_in(particles) for x in hop.groups()]

    hop.stop()

    return result

def plot_clumps(groups, total_mass):
    number_of_particles_in_group = []
    fraction_of_mass_in_group =  []

    for group in groups:
        number_of_particles_in_group.append(len(group))
        fraction = (group.mass.sum()/total_mass)
        fraction_of_mass_in_group.append(fraction)

    figure = pyplot.figure(figsize= (12,6))


    subplot = figure.add_subplot(1, 2, 1)

    colormap = pyplot.cm.Paired
    for index, group in enumerate(groups):
        color = colormap(1.0 * index / len(groups))
        subplot.scatter(
            group.x.value_in(units.parsec),
            group.y.value_in(units.parsec),
            s = group.mass.value_in(units.MSun),
            edgecolors = color,
            facecolors = color
        )

    subplot.set_xlim(0,1)
    subplot.set_ylim(0,1)
    subplot.set_xlabel('x (parsec)')
    subplot.set_ylabel('y (parsec)')

    subplot = figure.add_subplot(1, 2, 2)

    subplot.plot(
        number_of_particles_in_group,
        fraction_of_mass_in_group,
    )

    subplot.set_xscale('log')
    subplot.set_yscale('log')
    subplot.set_xlabel('N')
    subplot.set_ylabel('df/d(Log_10 N)')

    figure.savefig('x.png')
    pyplot.show()

if __name__ == "__main__":
    number_of_stars = 10000
    stars = new_cluster(number_of_stars)
    total_mass = stars.mass.sum()

    unit_converter = nbody_system.nbody_to_si(total_mass, 1 | units.parsec)
    groups = find_clumps(stars, unit_converter)
    plot_clumps(groups, total_mass)

Keywords: python, amuse, astrophysics, matplotlib, pylab, example, codex (see how-to-search-examples)

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