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# Copyright (c) 2017 Weitian LI <liweitianux@live.com>
# MIT license
"""
Merger tree that represents the merging history of a cluster using
the binary tree data structure.
"""
import os
import pickle
import logging
logger = logging.getLogger(__name__)
class MergerTree:
"""
A binary tree that represents the cluster merging history.
Description
-----------
Merged (M0, z0, age0)
~~~~~~~~~~~~~~~~~~~~~
/ \
Main (M1, z1, age1) Sub (M2, z2, age2)
~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~
* "Merged" is the merged cluster from "Main" and "Sub" at redshift
z1 (=z2) or cosmic time age1 (=age2).
M0 = M1 + M2, M1 > M2
* If "Sub" is missing, then this is an accretion event (not a merger).
Parameters
----------
data : dict
Data (e.g., mass, redshift, age) associated with this tree node.
main, sub : `~MergerTree`
Links to the main and sub (optional) clusters between which the
merger happens.
The ``sub`` cluster may be missing, which is regarded as an
accretion event rather than a merger.
merged : `~MergerTree`
Reverse link to the merged cluster. Therefore, it is able to refer
to the ``sub`` cluster from the ``main`` cluster, and vice versa.
"""
def __init__(self, data, main=None, sub=None, merged=None):
self.data = data
self.main = main
self.sub = sub
self.merged = merged
def save_mtree(mtree, outfile, clobber=False):
"""
Pickle the merger tree data and save to file.
"""
if os.path.exists(outfile):
if clobber:
os.remove(outfile)
logger.warning("Removed existing file: {0}".format(outfile))
else:
raise OSError("Output file already exists: {0}".format(outfile))
pickle.dump(mtree, open(outfile, "wb"))
logger.info("Saved merger tree to file: {0}".format(outfile))
def read_mtree(infile):
mtree = pickle.load(open(infile, "wb"))
logger.info("Loaded merger tree from file: {0}".format(infile))
return mtree
def plot_mtree(mtree):
"""
Plot the cluster merger tree.
"""
raise NotImplementedError
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