I successfully made the student BN example with PYMC3. It seems it gives the general answer correctly. [40%20AM] Is there an easy way to make a query for observation like {L=L0, S= S1} The code and CPDs are as follow: D = np.array([0.6, 0.4]) I = np.array([0.7, 0.3]) G = np.array([[[0.3, 0.4, 0.…

You can’t query the trace directly with ease. trace can either be given the variable’s name and find all values associated with it, or return the values of certain index in the trace. To easily query you can convert the trace to a pandas.DataFrame with pymc3.trace_to_dataframe. The Dataframe will ha…

I assume you mean to sample from the posterior. Can you explain more? and would you kindly send me the script of how you would set L==0 and S==1 and sample again from the posterior? Thanks Ramin

You mean, you would like to set evidence L = 0, and S = 1, and calculate posterior probabilities of other variables in the network P(D=1 | L = 0, S = 1)? It could be done like this: with pm.Model() as model: I_ = pm.Categorical('I', p=I) D_ = pm.Categorical('D', p=D) G_prob = T.shared(…

As @tomkov said, you can perform conditional sampling by setting some variables as observed. These variables will be fixed to 0 or 1 throughout the entire trace, so you cannot query values that are different from those. To get the probability of D=1 conditional on the observed L and S you can simply…

to be honest, i’m not getting the right results with that method. I’ve found somewhere on the Internet this example done with OpenBUGS: This was thair network: [image] [09] I’ve defined PCTs as: D = np.array([0.6, 0.4]) I = np.array([0.7, 0.3]) G = np.array([[[0.3, 0.7], [0.05,…

Thank you very much. shouldn’t it give me the same answer as the query method @lucianopaz suggested?

The example is taken from Koller’s book (Probabilistic graphical models Chapter 3) The difference in your setup and her example is G has 3 and CPD of L is little bit different. I tried using the posterior sampling using trace[‘D’] vs query method; I am getting the same answer with an error of thir…

I’ve tried both ways also, and compared them with Chpater 3, PGM Koller’s book. The thing is, in case when you use query method, you’ve already made assumption the prior probabilities in you network are correct, and therefore you can get examples from joint distribution. On the other hand, if you’…

Making a query for a simple BN made in PYMC3

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junpenglao February 5, 2019, 3:29pm 3

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Making a query for a simple BN made in PYMC3

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