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Python package for learning the graphical structure of Bayesian networks, parameter learning, inference and sampling methods.

Project description

bnlearn - Library for Bayesian network learning and inference

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bnlearn is Python package for learning the graphical structure of Bayesian networks, parameter learning, inference and sampling methods. This work is inspired by the R package (bnlearn.com) that has been very usefull to me for many years. Although there are very good Python packages for probabilistic graphical models, it still can remain difficult (and somethimes unnecessarily) to (re)build certain pipelines. Bnlearn for python (this package) is build on the pgmpy package and contains the most-wanted pipelines. Navigate to API documentations for more detailed information.

Method overview

Learning a Bayesian network can be split into the underneath problems which are all implemented in this package:

  • Structure learning: Given the data: Estimate a DAG that captures the dependencies between the variables.
  • Parameter learning: Given the data and DAG: Estimate the (conditional) probability distributions of the individual variables.
  • Inference: Given the learned model: Determine the exact probability values for your queries.

The following functions are available after installation:

# Import library
import bnlearn as bn

# Structure learning
bn.structure_learning.fit()

# Compute edge strength with the test statistic
bn.independence_test(model, df, test='chi_square', prune=True)

# Parameter learning
bn.parameter_learning.fit()

# Inference
bn.inference.fit()

# Make predictions
bn.predict()

# Based on a DAG, you can sample the number of samples you want.
bn.sampling()

# Load well known examples to play arround with or load your own .bif file.
bn.import_DAG()

# Load simple dataframe of sprinkler dataset.
bn.import_example()

# Compare 2 graphs
bn.compare_networks()

# Plot graph
bn.plot()

# To make the directed grapyh undirected
bn.to_undirected()

# Convert to one-hot datamatrix
bn.df2onehot()

# Derive the topological ordering of the (entire) graph 
bn.topological_sort()

# See below for the exact working of the functions

The following methods are also included:

  • inference
  • sampling
  • comparing two networks
  • loading bif files
  • conversion of directed to undirected graphs

Conda installation

It is advisable to create a new environment.

conda create -n env_bnlearn python=3.8
conda activate env_bnlearn

Pip installation

pip install bnlearn
  • Alternatively, install bnlearn from the GitHub source:
git clone https://github.com/erdogant/bnlearn.git
cd bnlearn
pip install -U .

Import bnlearn package

import bnlearn as bn

Example: Structure Learning

There are multiple manners to perform structure learning.

  • Exhaustivesearch
  • Hillclimbsearch
  • NaiveBayes
  • TreeSearch
    • Chow-liu
    • Tree-augmented Naive Bayes (TAN)
    import bnlearn as bn
    # Example dataframe sprinkler_data.csv can be loaded with: 
    df = bn.import_example()
    # df = pd.read_csv('sprinkler_data.csv')
    model = bn.structure_learning.fit(df)
    # Compute edge strength with the chi_square test statistic
    model = bn.independence_test(model, df)
    G = bn.plot(model)

df looks like this

     Cloudy  Sprinkler  Rain  Wet_Grass
0         0          1     0          1
1         1          1     1          1
2         1          0     1          1
3         0          0     1          1
4         1          0     1          1
..      ...        ...   ...        ...
995       0          0     0          0
996       1          0     0          0
997       0          0     1          0
998       1          1     0          1
999       1          0     1          1

  • Choosing various methodtypes and scoringtypes:
    model_hc_bic  = bn.structure_learning.fit(df, methodtype='hc', scoretype='bic')
    model_hc_k2   = bn.structure_learning.fit(df, methodtype='hc', scoretype='k2')
    model_hc_bdeu = bn.structure_learning.fit(df, methodtype='hc', scoretype='bdeu')
    model_ex_bic  = bn.structure_learning.fit(df, methodtype='ex', scoretype='bic')
    model_ex_k2   = bn.structure_learning.fit(df, methodtype='ex', scoretype='k2')
    model_ex_bdeu = bn.structure_learning.fit(df, methodtype='ex', scoretype='bdeu')
    model_cl      = bn.structure_learning.fit(df, methodtype='cl', root_node='Wet_Grass')
    model_tan     = bn.structure_learning.fit(df, methodtype='tan', root_node='Wet_Grass', class_node='Rain')

Example: Parameter Learning

    import bnlearn as bn
    # Import dataframe
    df = bn.import_example()
    # As an example we set the CPD at False which returns an "empty" DAG
    model = bn.import_DAG('sprinkler', CPD=False)
    # Now we learn the parameters of the DAG using the df
    model_update = bn.parameter_learning.fit(model, df)
    # Make plot
    G = bn.plot(model_update)

Example: Inference

    import bnlearn as bn
    model = bn.import_DAG('sprinkler')
    query = bn.inference.fit(model, variables=['Rain'], evidence={'Cloudy':1,'Sprinkler':0, 'Wet_Grass':1})
    print(query)
    print(query.df)
    
    # Lets try another inference
    query = bn.inference.fit(model, variables=['Rain'], evidence={'Cloudy':1})
    print(query)
    print(query.df)

Example: Sampling to create dataframe

    import bnlearn as bn
    model = bn.import_DAG('sprinkler')
    df = bn.sampling(model, n=1000)
  • Output of the model:
[bnlearn] Model correct: True
CPD of Cloudy:
+-----------+-----+
| Cloudy(0) | 0.5 |
+-----------+-----+
| Cloudy(1) | 0.5 |
+-----------+-----+
CPD of Sprinkler:
+--------------+-----------+-----------+
| Cloudy       | Cloudy(0) | Cloudy(1) |
+--------------+-----------+-----------+
| Sprinkler(0) | 0.5       | 0.9       |
+--------------+-----------+-----------+
| Sprinkler(1) | 0.5       | 0.1       |
+--------------+-----------+-----------+
CPD of Rain:
+---------+-----------+-----------+
| Cloudy  | Cloudy(0) | Cloudy(1) |
+---------+-----------+-----------+
| Rain(0) | 0.8       | 0.2       |
+---------+-----------+-----------+
| Rain(1) | 0.2       | 0.8       |
+---------+-----------+-----------+
CPD of Wet_Grass:
+--------------+--------------+--------------+--------------+--------------+
| Sprinkler    | Sprinkler(0) | Sprinkler(0) | Sprinkler(1) | Sprinkler(1) |
+--------------+--------------+--------------+--------------+--------------+
| Rain         | Rain(0)      | Rain(1)      | Rain(0)      | Rain(1)      |
+--------------+--------------+--------------+--------------+--------------+
| Wet_Grass(0) | 1.0          | 0.1          | 0.1          | 0.01         |
+--------------+--------------+--------------+--------------+--------------+
| Wet_Grass(1) | 0.0          | 0.9          | 0.9          | 0.99         |
+--------------+--------------+--------------+--------------+--------------+
[bnlearn] Nodes: ['Cloudy', 'Sprinkler', 'Rain', 'Wet_Grass']
[bnlearn] Edges: [('Cloudy', 'Sprinkler'), ('Cloudy', 'Rain'), ('Sprinkler', 'Wet_Grass'), ('Rain', 'Wet_Grass')]
[bnlearn] Independencies:
(Cloudy _|_ Wet_Grass | Rain, Sprinkler)
(Sprinkler _|_ Rain | Cloudy)
(Rain _|_ Sprinkler | Cloudy)
(Wet_Grass _|_ Cloudy | Rain, Sprinkler)

Example: Loading DAG from bif files

    import bnlearn as bn
    
    bif_file= 'sprinkler'
    bif_file= 'alarm'
    bif_file= 'andes'
    bif_file= 'asia'
    bif_file= 'pathfinder'
    bif_file= 'sachs'
    bif_file= 'miserables'
    bif_file= 'filepath/to/model.bif'
    
    # Loading example dataset
    model = bn.import_DAG(bif_file)

Example: Comparing networks

    # Load asia DAG
    model = bn.import_DAG('asia')
    # plot ground truth
    G = bn.plot(model)
    # Sampling
    df = bn.sampling(model, n=10000)
    # Structure learning of sampled dataset
    model_sl = bn.structure_learning.fit(df, methodtype='hc', scoretype='bic')
    # Compute edge strength with the chi_square test statistic
    model_sl = bn.independence_test(model_sl, df, test='chi_square', prune=True)
    # Plot based on structure learning of sampled data
    bn.plot(model_sl, pos=G['pos'])
    # Compare networks and make plot
    bn.compare_networks(model, model_sl, pos=G['pos'])

Graph of ground truth

Graph based on Structure learning

Graph comparison ground truth vs. structure learning

Example: Titanic example

    import bnlearn as bn
    
    # Load example mixed dataset
    df = bn.import_example(data='titanic')

    # Convert to onehot
    dfhot, dfnum = bn.df2onehot(df)

    # Structure learning
    # model = bn.structure_learning.fit(dfnum, methodtype='cl', black_list=['Embarked','Parch','Name'], root_node='Survived', bw_list_method='nodes')
    model = bn.structure_learning.fit(dfnum)
    # Plot
    G = bn.plot(model, interactive=False)

    # Compute edge strength with the chi_square test statistic
    model = bn.independence_test(model, dfnum, test='chi_square', prune=True)
    # Plot
    bn.plot(model, interactive=False, pos=G['pos'])

    # Parameter learning
    model = bn.parameter_learning.fit(model, dfnum)
    
    # Make inference
    query = bn.inference.fit(model, variables=['Survived'], evidence={'Sex':True, 'Pclass':True})
    print(query)
    print(query.df)
    
    # Another inference using only sex for evidence
    query = bn.inference.fit(model, variables=['Survived'], evidence={'Sex':0})
    print(query)
    print(query.df)
    
    # Print model
    bn.print_CPD(model)

Plot DAG

Example: Make predictions on a dataframe using inference

    # Import bnlearn
    import bnlearn as bn
    
    # Load example DataFrame
    df = bn.import_example('asia')

    print(df)
    #       smoke  lung  bronc  xray
    # 0         0     1      0     1
    # 1         0     1      1     1
    # 2         1     1      1     1
    # 3         1     1      0     1
    # 4         1     1      1     1
    #     ...   ...    ...   ...
    # 9995      1     1      1     1
    # 9996      1     1      1     1
    # 9997      0     1      1     1
    # 9998      0     1      1     1
    # 9999      0     1      1     0

    # Create some edges for the DAG
    edges = [('smoke', 'lung'),
             ('smoke', 'bronc'),
             ('lung', 'xray'),
             ('bronc', 'xray')]
    
    # Construct the Bayesian DAG
    DAG = bn.make_DAG(edges, verbose=0)
    # Plot DAG
    bn.plot(DAG)

    # Learn CPDs using the DAG and dataframe
    model = bn.parameter_learning.fit(DAG, df, verbose=3)
    bn.print_CPD(model)

    # CPD of smoke:
    # +----------+----------+
    # | smoke(0) | 0.500364 |
    # +----------+----------+
    # | smoke(1) | 0.499636 |
    # +----------+----------+
    # CPD of lung:
    # +---------+---------------------+----------------------+
    # | smoke   | smoke(0)            | smoke(1)             |
    # +---------+---------------------+----------------------+
    # | lung(0) | 0.13753633720930233 | 0.055131004366812224 |
    # +---------+---------------------+----------------------+
    # | lung(1) | 0.8624636627906976  | 0.9448689956331878   |
    # +---------+---------------------+----------------------+
    # CPD of bronc:
    # +----------+--------------------+--------------------+
    # | smoke    | smoke(0)           | smoke(1)           |
    # +----------+--------------------+--------------------+
    # | bronc(0) | 0.5988372093023255 | 0.3282387190684134 |
    # +----------+--------------------+--------------------+
    # | bronc(1) | 0.4011627906976744 | 0.6717612809315866 |
    # +----------+--------------------+--------------------+
    # CPD of xray:
    # +---------+---------------------+---------------------+---------------------+---------------------+
    # | bronc   | bronc(0)            | bronc(0)            | bronc(1)            | bronc(1)            |
    # +---------+---------------------+---------------------+---------------------+---------------------+
    # | lung    | lung(0)             | lung(1)             | lung(0)             | lung(1)             |
    # +---------+---------------------+---------------------+---------------------+---------------------+
    # | xray(0) | 0.7787162162162162  | 0.09028393966282165 | 0.7264957264957265  | 0.07695139911634757 |
    # +---------+---------------------+---------------------+---------------------+---------------------+
    # | xray(1) | 0.22128378378378377 | 0.9097160603371783  | 0.27350427350427353 | 0.9230486008836525  |
    # +---------+---------------------+---------------------+---------------------+---------------------+
    # [bnlearn] >Independencies:
    # (smoke ⟂ xray | bronc, lung)
    # (lung ⟂ bronc | smoke)
    # (bronc ⟂ lung | smoke)
    # (xray ⟂ smoke | bronc, lung)
    # [bnlearn] >Nodes: ['smoke', 'lung', 'bronc', 'xray']
    # [bnlearn] >Edges: [('smoke', 'lung'), ('smoke', 'bronc'), ('lung', 'xray'), ('bronc', 'xray')]


    # Generate some example data based on DAG
    Xtest = bn.sampling(model, n=1000)
    print(Xtest)
    #      smoke  lung  bronc  xray
    # 0        1     1      1     1
    # 1        1     1      1     1
    # 2        0     1      1     1
    # 3        1     0      0     1
    # 4        1     1      1     1
    # ..     ...   ...    ...   ...
    # 995      1     1      1     1
    # 996      1     1      1     1
    # 997      0     1      0     1
    # 998      0     1      0     1
    # 999      0     1      1     1
    

    # Make predictions
    Pout = bn.predict(model, Xtest, variables=['bronc','xray'])
    print(Pout)

    #         xray  bronc         p
    # 0       1      0  0.542757
    # 1       1      1  0.624117
    # 2       1      0  0.542757
    # 3       1      1  0.624117
    # 4       1      0  0.542757
    # ..    ...    ...       ...
    # 995     1      0  0.542757
    # 996     1      0  0.542757
    # 997     1      1  0.624117
    # 998     1      1  0.624117
    # 999     1      0  0.542757

    

Example of interactive plotting

    import bnlearn as bn
    df = bn.import_example()

    # Structure learning
    model = bn.structure_learning.fit(df)


    # Add some parameters for the interactive plot
    bn.plot(model, interactive=True, params_interactive = {'height':'600px'})

    # Add more parameters for the interactive plot
    bn.plot(model, interactive=True, params_interactive = {'directed':True, 'height':'800px', 'width':'70%', 'notebook':False, 'heading':'bnlearn title', 'layout':None, 'font_color': False, 'bgcolor':'#ffffff'})

Example of interactive and static plotting

In case of static plotting, simply set the interactive parameter to False.

    import bnlearn as bn
    df = bn.import_example(data='asia')
    
    # Structure learning
    model = bn.structure_learning.fit(df)
    
    # Compute edge strength with the chi_square test statistic
    model = bn.independence_test(model, df, test='chi_square', prune=True)
    
    # Make simple interactive plot
    bn.plot(model, interactive=False)
    
    # Make simple interactive plot, set color to entire network
    bn.plot(model, node_color='#8A0707', interactive=True)
    
    # Make simple interactive plot, set color and size to entire network
    bn.plot(model, node_color='#8A0707', node_size=25, interactive=True)
    
    # Set some edge properties
    edge_properties = bn.get_edge_properties(model)
    edge_properties['either', 'xray']['color']='#8A0707'
    edge_properties['either', 'xray']['weight']=4
    edge_properties['bronc', 'dysp']['weight']=15
    edge_properties['bronc', 'dysp']['color']='#8A0707'
    
    # Set some node properties
    node_properties = bn.get_node_properties(model)
    node_properties['xray']['node_color']='#8A0707'
    node_properties['xray']['node_size']=20
    
    # Add more parameters for the interactive plot
    bn.plot(model, interactive=True, node_color='#8A0707', node_properties=node_properties, edge_properties=edge_properties, params_interactive = {'height':'800px', 'width':'70%', 'layout':None, 'bgcolor':'#0f0f0f0f'})
    
    # Add more parameters for the static plot
    bn.plot(model, interactive=False, node_color='#8A0707', node_size=800, node_properties=node_properties, edge_properties=edge_properties, params_static = {'width':15, 'height':8, 'font_size':14, 'font_family':'times new roman', 'alpha':0.8, 'node_shape':'o', 'facecolor':'white', 'font_color':'#000000', 'edge_alpha':0.6, 'arrowstyle':'->', 'arrowsize':60})
    
    # You can also add some parameters for the interactive plot
    bn.plot(model, interactive=True, params_interactive = {'height':'600px'})

Example of saving and loading models

    # Load data
    # Import example
    df = bn.import_example(data='asia')
    # Learn structure
    model = bn.structure_learning.fit(df, methodtype='tan', class_node='lung')
    # Save model
    bn.save(model, filepath='bnlearn_model', overwrite=True)
    # Load model
    model = bn.load(filepath='bnlearn_model')

References

Maintainer

Erdogan Taskesen, github: [erdogant](https://github.com/erdogant)
Please cite in your publications if this is useful for your research (see citation).
All kinds of contributions are welcome!
If you wish to buy me a <a href="https://www.buymeacoffee.com/erdogant">Coffee</a> for this work, it is very appreciated :)
See [LICENSE](LICENSE) for details.

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