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Old engine for Continuous Time Bayesian Networks. Superseded by reCTBN. 🐍 https://github.com/madlabunimib/PyCTBN
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README.rst

PyCTBN
======

.. image:: https://codecov.io/gh/madlabunimib/PyCTBN/branch/master/graph/badge.svg
:target: https://codecov.io/gh/madlabunimib/PyCTBN




A Continuous Time Bayesian Networks Library

Installation/Usage
*******************

The library has been tested on Linux and Windows with Python 3.8 and it relies on the following Python modules:

- numpy
- pandas
- networkx
- scipy
- matplotlib
- tqdm

**Pip installation**

Download the latest release in .tar.gz or .whl format and simply use pip install to install it:

$ pip install PyCTBN-2.2.tar.gz

Documentation
*************
Please refer to https://madlabunimib.github.io/PyCTBN/ for the full project documentation.

Implementing your own data importer
***********************************
| This example demonstrates the implementation of a simple data importer the extends the class AbstractImporter
| to import data in csv format. The net in exam has three ternary nodes and no prior net structure.
| Suppose the trajectories that have to be inported have this structure:

.. image:: docs-out/esempio_dataset.png
:width: 600
:alt: An example trajectory to be imported.

| In the read_csv_file method the data are imported in memory, put in a list and assigned to the _df_samples_list class
| member, so that it contains all the trajectories to be processed.
| In the import_variables method the dataframe containing the nodes labels and the cardinalities of the nodes
| is assigned to the _df_variables class member.
| The class member _sorter has to contain the nodes labels in the same order of the trajectory columns,
| just override the build_sorter method to do that.
| If your datasets names have particular id, you can keep it using the dataset_id method to assign the id to a new class member.
| Finally the import_data method call all the previously implemented methods and calls the compute_row_delta_in_all_samples_frames
| to process all the trajectories in _df_samples_list.
| For more information about the class memebers and methods of AbstractImporter please refer to the documentation.

.. code-block:: python

import pandas as pd
import typing

from PyCTBN import AbstractImporter
from PyCTBN import SamplePath

class CSVImporter(AbstractImporter):

def __init__(self, file_path):
self._df_samples_list = None
super(CSVImporter, self).__init__(file_path)

def import_data(self):
self.read_csv_file()
self._sorter = self.build_sorter(self._df_samples_list[0])
self.import_variables()
self.compute_row_delta_in_all_samples_frames(self._df_samples_list)

def read_csv_file(self):
df = pd.read_csv(self._file_path)
df.drop(df.columns[[0]], axis=1, inplace=True)
self._df_samples_list = [df]

def import_variables(self):
values_list = [3 for var in self._sorter]
# initialize dict of lists
data = {'Name':self._sorter, 'Value':values_list}
# Create the pandas DataFrame
self._df_variables = pd.DataFrame(data)

def build_sorter(self, sample_frame: pd.DataFrame) -> typing.List:
return list(sample_frame.columns)[1:]

def dataset_id(self) -> object:
pass

def main():
# create the importer object
csvimp = CSVImporter('/dataset_example.csv')
# call the wrapping method that wil import and process the data
csvimp.import_data()
# pass the AbstractImporter object to the SamplePath constructor
s1 = SamplePath(csvimp)
# SamplePath will contain the Trajecotry object...
s1.build_trajectories()
#...and the Structure object with all the process data
s1.build_structure()


Structure Estimation Examples
##############################

| In this section some examples will be shown in order to provide some useful information about the usage of the library


Constraint based estimation
****************************
| This example shows how to estimate the structure given a series of trajectories using a constraint based approach.
| The first three instructions import all the necessary data (trajectories, nodes cardinalities, nodes labels),
| and are contextual to the dataset that is been used, in the code comments are marked as optional <>.
| If your data has a different structure or format you should implement your own importer
| (see Implementing your own importer example).
| The other instructions are not optional and should follow the same order.
| A SamplePath object is been created, passing an AbstractImporter object that contains the correct class members
| filled with the data that are necessary to estimate the structure.
| Next the build_trajectories and build_structure methods are called to instantiate the objects that will contain
| the processed trajectories and all the net information.
| Then an estimator object is created, in this case a constraint based estimator,
| it necessary to pass a SamplePath object where build_trajectories and build_structure methods have already been called.
| If you have prior knowledge about the net structure pass it to the constructor with the known_edges parameter.
| The other three parameters are contextual to the StructureConstraintBasedEstimator, see the documentation for more details.
| To estimate the structure simply call the estimate_structure method.
| You can obtain the estimated structure as a boolean adjacency matrix with the method adjacency_matrix,
| or save it as a json file that contains all the nodes labels, and obviously the estimated edges.
| You can also save a graphical model representation of the estimated structure
| with the save_plot_estimated_structure_graph.

.. code-block:: python

import glob
import os

from PyCTBN import JsonImporter
from PyCTBN import SamplePath
from PyCTBN import StructureConstraintBasedEstimator


def structure_constraint_based_estimation_example():
# <read the json files in ./data path>
read_files = glob.glob(os.path.join('./data', "*.json"))
# <initialize a JsonImporter object for the first file>
importer = JsonImporter(file_path=read_files[0], samples_label='samples',
structure_label='dyn.str', variables_label='variables',
time_key='Time', variables_key='Name')
# <import the data at index 0 of the outer json array>
importer.import_data(0)
# construct a SamplePath Object passing a filled AbstractImporter object
s1 = SamplePath(importer=importer)
# build the trajectories
s1.build_trajectories()
# build the information about the net
s1.build_structure()
# construct a StructureEstimator object passing a correctly build SamplePath object
# and the independence tests significance, if you have prior knowledge about
# the net structure create a list of tuples
# that contains them and pass it as known_edges parameter
se1 = StructureConstraintBasedEstimator(sample_path=s1, exp_test_alfa=0.1, chi_test_alfa=0.1,
known_edges=[], thumb_threshold=25)
# call the algorithm to estimate the structure
se1.estimate_structure()
# obtain the adjacency matrix of the estimated structure
print(se1.adjacency_matrix())
# save the estimated structure to a json file
# (remember to specify the path AND the .json extension)....
se1.save_results('./results0.json')
# ...or save it also in a graphical model fashion
# (remember to specify the path AND the .png extension)
se1.save_plot_estimated_structure_graph('./result0.png')



Score based estimation with Hill Climbing
*****************************************

| This example shows how to estimate the structure given a series of trajectories using a score based approach
| and the Hill Climbing algorithm as optimization strategy.
| The structure of the code is the same as the previus example, but an explanation of the Structure score based estimator
| will be provided.
| Then an estimator object is created, in this case a score based estimator,
| it necessary to pass a SamplePath object where build_trajectories and build_structure methods have already been called.
| If you have prior knowledge about the net structure pass it to the constructor with the known_edges parameter.
| The other parameters are contextual to the StructureScoreBasedEstimator, see the documentation for more details.
| To estimate the structure simply call the estimate_structure method passing the desidered parameters, such as the
| optimization strategy, or simply use the default configuration.
| In this case an Hill Climbing approch is choosen.

.. code-block:: python

import glob
import os

from PyCTBN import JsonImporter
from PyCTBN import SamplePath
from PyCTBN import StructureScoreBasedEstimator


def structure_constraint_based_estimation_example():
# <read the json files in ./data path>
read_files = glob.glob(os.path.join('./data', "*.json"))
# <initialize a JsonImporter object for the first file>
importer = JsonImporter(file_path=read_files[0], samples_label='samples',
structure_label='dyn.str', variables_label='variables',
time_key='Time', variables_key='Name')
# <import the data at index 0 of the outer json array>
importer.import_data(0)
# construct a SamplePath Object passing a filled AbstractImporter object
s1 = SamplePath(importer=importer)
# build the trajectories
s1.build_trajectories()
# build the information about the net
s1.build_structure()
# construct a StructureEstimator object passing a correctly build SamplePath object
# and hyperparameters tau and alpha, if you have prior knowledge about
# the net structure create a list of tuples
# that contains them and pass it as known_edges parameter
se1 = StructureScoreBasedEstimator(sample_path=s1, tau_xu = 0.1, alpha_xu = 1,
known_edges=[])
# call the algorithm to estimate the structure
# and pass all the desidered parameters, in this case an Hill Climbing approach
# will be selected as optimization strategy.
se1.estimate_structure(
max_parents = None,
iterations_number = 40,
patience = None,
optimizer = 'hill'
)
# obtain the adjacency matrix of the estimated structure
print(se1.adjacency_matrix())
# save the estimated structure to a json file
# (remember to specify the path AND the .json extension)....
se1.save_results('./results0.json')
# ...or save it also in a graphical model fashion
# (remember to specify the path AND the .png extension)
se1.save_plot_estimated_structure_graph('./result0.png')


Score based estimation with Tabu Search and Data Augmentation
**************************************************************

| This example shows how to estimate the structure given a series of trajectories using a score based approach
| and the Tabu Search algorithm as optimization strategy and how to use a data augmentation strategy to increase the
| number of data available.
| The structure of the code is the same as the previus example, but an explanation of the data augmentation technique
| will be provided.
| In this case a SampleImporter is used to import the data instead of a JsonImporter.
| Using a SampleImporter requires the user to read the data and put it into different lists or DataFrames before to
| inizialize the SampleImporter instance.
| Then it is possible to increase the amount of data by using one of the external libraries who provide data augmentation
| approaches, in this example sklearn is used.
| Then all the information can be passed to the SampleImporter constructor and the import_data method can be used to provide
| the preprossing operations of the PyCTBN library.
| Then an estimator object is created, in this case a score based estimator,
| it necessary to pass a SamplePath object where build_trajectories and build_structure methods have already been called.
| If you have prior knowledge about the net structure pass it to the constructor with the known_edges parameter.
| The other parameters are contextual to the StructureScoreBasedEstimator, see the documentation for more details.
| To estimate the structure simply call the estimate_structure method passing the desidered parameters, such as the
| optimization strategy, or simply use the default configuration.
| In this case an Hill Climbing approch is choosen.


.. code-block:: python

import glob
import os

from sklearn.utils import resample

from PyCTBN import SampleImporter
from PyCTBN import SamplePath
from PyCTBN import StructureScoreBasedEstimator


def structure_constraint_based_estimation_example():
# <read the json files in ./data path>
read_files = glob.glob(os.path.join('./data', "*.json"))

# read the first file in the directory (or pass the file path)
with open(file_path=read_files[0]) as f:
raw_data = json.load(f)

# read the variables information
variables= pd.DataFrame(raw_data[0]["variables"])

# read the prior information if they are given
prior_net_structure = pd.DataFrame(raw_data[0]["dyn.str"])

#read the samples
trajectory_list_raw= raw_data[0]["samples"]

#convert them in DataFrame
trajectory_list = [pd.DataFrame(sample) for sample in trajectory_list_raw]

# use an external library in order to provide the data augmentation operations, in this case
# sklearn.utils is used
augmented_trajectory_list = resample (trajectory_list, replace = True, n_samples = 300 )


# <initialize a SampleImporter object using the data read before>
importer = SampleImporter(
trajectory_list = augmented_trajectory_list,
variables=variables,
prior_net_structure=prior_net_structure
)

# <import the data>
importer.import_data()
# construct a SamplePath Object passing a filled AbstractImporter object

s1 = SamplePath(importer=importer)
# build the trajectories
s1.build_trajectories()
# build the information about the net
s1.build_structure()
# construct a StructureEstimator object passing a correctly build SamplePath object
# and hyperparameters tau and alpha, if you have prior knowledge about
# the net structure create a list of tuples
# that contains them and pass it as known_edges parameter
se1 = StructureScoreBasedEstimator(sample_path=s1, tau_xu = 0.1, alpha_xu = 1,
known_edges=[])
# call the algorithm to estimate the structure
# and pass all the desidered parameters, in this case a Tabu Search approach
# will be selected as optimization strategy. It is possible to select the tabu list length and
# the tabu rules duration, and the other parameters as in the previus example.
se1.estimate_structure(
max_parents = None,
iterations_number = 100,
patience = 20,
optimizer = 'tabu',
tabu_length = 10,
tabu_rules_duration = 10
)
# obtain the adjacency matrix of the estimated structure
print(se1.adjacency_matrix())
# save the estimated structure to a json file
# (remember to specify the path AND the .json extension)....
se1.save_results('./results0.json')
# ...or save it also in a graphical model fashion
# (remember to specify the path AND the .png extension)
se1.save_plot_estimated_structure_graph('./result0.png')