/// <summary>
/// Creates a Bayesian Network from a given DagPattern which has to be a DAG and uses the given distributions if they fit the DAG structure.
/// </summary>
/// <exception cref="ArgumentException">Thrown when the given DagPattern is no DAG or the distributions don't fit the DAG structure</exception>
public static BayesianNetwork FromDagPattern(DagPattern <RandomVariable> dag, IEnumerable <ProbabilityDistribution> distributions)
{
if (!dag.IsDag())
{
throw new ArgumentException("BayesianNetworks need a DAG, but the given DAG was actually a DAG pattern!");
}
var network = new BayesianNetwork(dag);
var processed = new bool[network.RandomVariables.Count];
foreach (var distribution in distributions)
{
var rvar = distribution.RandomVariable;
var parents = dag.GetParents(rvar);
// do the conditions fit with the dag structure?
if (parents.Except(distribution.Conditions).Any() || parents.Count != distribution.Conditions.Count)
{
throw new ArgumentException($"The random variable {rvar.Name} has parents {string.Join(",", parents)} but conditions {string.Join(",", distribution.Conditions)}");
}
network.Distributions[rvar] = distribution;
processed[network.RandomVariables.IndexOf(rvar)] = true;
// fill distributions in random variables without parents
if (parents.Count == 0)
{
rvar.Probability = distribution.Distribution;
}
}
if (!processed.All(p => p))
{
throw new ArgumentException("The given probability distribution did not include all random variables!");
}
return(network);
}
public ConstraintBasedStructureLearner(IList <RandomVariable> randomVariables, DualKeyDictionary <RandomVariable, ICollection <ISet <RandomVariable> > > independencies)
{
_randomVariables = randomVariables;
_independencies = independencies;
_dag = DagPattern <RandomVariable> .InitCompleteDag(randomVariables);
_collectedConditions = new DualKeyDictionary <RandomVariable, ISet <RandomVariable> >();
foreach (var x in _dag.Nodes)
{
foreach (var y in _dag.Nodes.Where(y => x != y))
{
_collectedConditions[x, y] = new HashSet <RandomVariable>();
}
}
}
/// <summary>
/// Creates a Bayesian Network from a given DagPattern which has to be a DAG and calculates the conditional distributions according to the DAG structure.
/// </summary>
/// <exception cref="ArgumentException">Thrown when the given DagPattern is no DAG</exception>
public static BayesianNetwork FromDagPattern(DagPattern <RandomVariable> dag, IProbabilityDistributionCalculator calc)
{
if (!dag.IsDag())
{
throw new ArgumentException("BayesianNetworks need a DAG, but the given DAG was actually a DAG pattern!");
}
var network = new BayesianNetwork(dag);
foreach (var rvar in dag.Nodes)
{
var parents = dag.GetParents(rvar).ToList();
var distribution = calc.CalculateConditionalProbabilityDistribution(rvar, parents);
network.Distributions[rvar] = new ProbabilityDistribution(rvar, parents, distribution);
}
return(network);
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
var randomVariableNames = _randomVariables.Select(rvar => rvar.Name).ToList();
var randomVariableMapping = new Dictionary <string, RandomVariable>();
foreach (var randomVariable in _randomVariables)
{
randomVariableMapping[randomVariable.Name] = randomVariable;
}
var json = JObject.Load(reader);
// construct DagPattern
var dag = json.Property(DagProperty);
var edges = dag.Value.Value <JArray>(EdgesProperty).ToObject <int[]>();
var nodes = dag.Value.Value <JArray>(NodesProperty).ToObject <string[]>();
var realEdges = new int[nodes.Length, nodes.Length];
for (var i = 0; i < nodes.Length; i++)
{
for (var j = 0; j < nodes.Length; j++)
{
// given random variables could be in another order, so lookup the index
realEdges[randomVariableNames.IndexOf(nodes[i]), randomVariableNames.IndexOf(nodes[j])] = edges[i * nodes.Length + j];
}
}
var dagPattern = DagPattern <RandomVariable> .InitDagWithMatrix(_randomVariables, realEdges);
// construct probability distributions
var distributions = json.Property(DistributionsProperty).Value.Children();
var realDistributions = new List <ProbabilityDistribution>();
foreach (var distribution in distributions)
{
var randomVariable = distribution.Value <string>(RandomVariableProperty);
var realRandomVariable = randomVariableMapping[randomVariable];
var conditions = distribution.Value <JArray>(ConditionsProperty).ToObject <string[]>();
var realConditions = conditions.Select(condition => randomVariableMapping[condition]).ToList();
var distributionValues = distribution.Value <JArray>(DistributionProperty).ToObject <double[]>();
var realDistributionValues = distributionValues.Select(distValue => new Probability(distValue)).ToList();
realDistributions.Add(new ProbabilityDistribution(realRandomVariable, realConditions, realDistributionValues));
}
return(BayesianNetwork.FromDagPattern(dagPattern, realDistributions));
}
private BayesianNetwork ToBayesianNetwork(BayesianNetworkResult result)
{
var allVariables = MapToAllVariables();
var nodes = result.Nodes.Select(node => allVariables[node]).ToList();
var dag = DagPattern <RandomVariable> .InitEmptyDag(nodes);
foreach (var arc in result.Arcs)
{
dag.AddEdge(allVariables[arc.From], allVariables[arc.To]);
}
var distributions = new List <ProbabilityDistribution>();
foreach (var probTable in result.ProbTables)
{
var rvar = allVariables[probTable.Rvar.First()];
var conditions = probTable.Conditions.Select(condition => allVariables[condition]).ToList();
var probabilities = ToProbabilityArray(probTable.Probs, conditions.Count + 1);
distributions.Add(new ProbabilityDistribution(rvar, conditions, probabilities));
}
return(BayesianNetwork.FromDagPattern(dag, distributions));
}
private BayesianNetwork(DagPattern <RandomVariable> dag)
{
Dag = dag;
Distributions = new Dictionary <RandomVariable, ProbabilityDistribution>();
}