Population

class sorts.population.population.Population(fields=None, dtypes=None, space_object_fields=None, state_fields=None, epoch_field=None, propagator=None, propagator_args={}, propagator_options={})[source]

Bases: object

Encapsulates a population of space objects as an array and functions for returning instances of space objects.

Default columns:

  • 0: oid - Object ID

  • 1: a - Semi-major axis in m

  • 2: e - Eccentricity

  • 3: i - Inclination in degrees

  • 4: raan - Right Ascension of ascending node in degrees

  • 5: aop - Argument of perihelion in degrees

  • 6: mu0 - Mean anoamly in degrees

  • 7: mjd0 - Epoch of object given in Modified Julian Days

Any column that is added will have its name used in initializing the Space object.

A population’s column data can also be accessed as a python dictionary or a table according to row number, e.g.

#this returns all Right Ascension of ascending node as a numpy vector
vector = my_population['raan']

#this gets row number 3 (since we use 0 indexing)
row = my_population[2]

but it is also configured to be able to try to convert to uniform type array and perform numpy like slices. If a column data type cannot be converted to the default data type numpy.nan is inserted instead.

#This will convert the internal data structure to a uniform type array and select all rows and columns 4 and onwards. This is time-consuming on large populations as it actually copies to data.
vector = my_population[:,4:]

# This is significantly faster as a single column is easy to extract and no conversion is needed
data_point = my_population[123,2]

This indexing system can also be used for data manipulation:

my_population['raan'] = vector
my_population[2] = row
my_population[:,4:] = matrix
my_population[123,2] = 2.3
my_population[123,11] = 'test'

Notice that in the above example the value to be assigned always has the correct size corresponding to the index and slices, a statement like x[:,3:7] = 3 is not possible, instead one would write x[:,3:7] = np.full((len(pop), 4), 3.0, dtype='f').

#TODO: THESE HAVE CHANGED, UPDATE THEM!!!!

Variables

  • objs (numpy.ndarray) – Array containing population data. Rows correspond to objects and columns to variables.

  • name (str) – Name of population.

  • fields (list) – List of strings containing column descriptions.

  • space_object_uses (list) – List of booleans describing what columns should be included when initializing a space object. This allows for extra data to be stored in the population without passing it to the space object.

  • propagator (PropagatorBase) – Propagator class pointer used for space_object.SpaceObject.

  • propagator_options (dict) – Propagator initialization keyword arguments.

Parameters

  • name (str) – Name of population.

  • fields (list) – List of strings containing column descriptions for addition data besides the default columns.

  • dtypes (list) – List of strings containing numpy data type description. Defaults to ‘f’.

  • space_object_fields (list) – List of booleans describing what columns should be included when initializing a space object. This allows for extra data to be stored in the population without passing it to the space object.

  • propagator (PropagatorBase) – Propagator class pointer used for space_object.SpaceObject.

  • propagator_options (dict) – Propagator initialization keyword arguments.

Methods

__init__([fields, dtypes, …])

Initialize self.

add_field(name[, dtype])

Add a field to the population data.

allocate(length)

Allocate the internal data array for assignment of objects.

copy()

Return a copy of the current Population instance.

delete(inds)

Remove the rows according to the given indices.

filter(col, fun)

Filters the population using a boolean function, keeping true values.

get_fields(fields[, n, named, dtype])

Get the orbital elements for one row from internal data array.

get_object(n)

Get the one row from the population as a space_object.SpaceObject instance.

get_orbit(n[, fields, M_cent, degrees, anomaly])

Get the one row from the population as a pyorb.Orbit instance.

get_states([n, named, dtype])

Use the defined state parameters to get a copy of the states

load(fname, propagator[, …])

next()

print([n, fields])

save(fname)

Attributes

generator

in_frame

out_frame

shape

This is the shape of the internal data matrix