DBN: CPD associated with (B, 1) doesn't have proper parents associated with it.

[tomorrown]

Subject of the issue

A Dynamic Bayesian network is built, but the network is always displayed: CPD associated with (B, 1) doesn't have proper parents associated with it.

Your environment

• pgmpy version

Steps to reproduce

from pgmpy.factors.discrete import TabularCPD
from pgmpy.models import DynamicBayesianNetwork as DBN
from pgmpy.inference import DBNInference

dbnet = DBN()
dbnet.add_edges_from(
[(('A', 0), ('B', 0)), (('A', 0), ('C', 0)),
(('C', 0), ('D', 0)), (('B', 0), ('B', 1)),
(('B', 0), ('D', 1 ))
]
)
a_cpds = TabularCPD(('A', 0), 2, [[0.7], [0.3]])
b_start_cpds = TabularCPD(
('B', 0), 2, [[0.3, 0.6],
[0.7, 0.4]],
evidence=[('A', 0)],
evidence_card=[2]
)
b_trans_cpds = TabularCPD(
('B',1), 2, [[0.1, 0.3, 0.8, 0.6],
[0.9, 0.7, 0.2, 0.4]],
evidence=[('A', 0), ('B', 0)],
evidence_card=[2, 2]
)
c_cpds = TabularCPD(
('C', 0), 2, [[0.3, 0.1],
[0.7,0.9]],
evidence=[('A', 0)],
evidence_card=[2]
)
d_start_cpds = TabularCPD(
('D',0), 2, [[0.4, 0.2], [0.6, 0.8]],
evidence=[('C', 0)],
evidence_card=[2]
)
d_trans_cpds = TabularCPD(
('D',1), 2, [[0.3, 0.4, 0.8, 0.9],
[0.7, 0.6, 0.2, 0.1]],
evidence=[('B', 0),('C',0)],
evidence_card=[2, 2]
)
dbnet.add_cpds(a_cpds, b_start_cpds, b_trans_cpds, c_cpds, d_start_cpds, d_trans_cpds)
dbnet.initialize_initial_state()
dbn_inf = DBNInference(dbnet)
temp = dbn_inf.query([('D', 1)], {('D', 0):0, ('D', 2):1})['D', 1].values
print(temp)

Expected behaviour

When the evidence under the first time slice of D is true and the evidence under the third time slice is false, the probability of the second time slice is calculated by reasoning. The final calculation result is D2, True: 0.7365902, False:0.2634098

Actual behaviour

CPD associated with (B, 1) doesn't have proper parents associated with it. Is this a problem of network model building? Specific network diagram, see [https://www.bilibili.com/video/BV1W3411M7cp/?spm_id_from=333.337.search-card.all.click&vd_source=1a42ddbfb403e da9de41b20ccdca8523]

[ankurankan]

@tomorrown I think there is a slight mistake in the CPDs that you have defined. For variables (D, 1) and (B, 1), the evidence variables should be [(B, 0), (C, 1)] and [(A, 1), (B, 0)]. If you fix this, the model definition seems to work for me. The inference still is throwing an error, and I am still looking into it.