observed=True real understanding?

Questions v5
1

observation = pm.Poisson(“obs”, lambda_, value=count_data,
observed=True)

I am trying to model possion distribution and not able to understand what really oberserve=true do and what is its inference in terms of understanding?

2

observed=True, will be converted to observed=1, meaning one observation with value of 1. In general observed is not a boolean flag but the values that were observed for that variable.

3

Thanks for your reply. I am going through a book and in that it is mentioned as :

We also set observed = True to tell PyMC that this should stay fixed in our analysis

Is it means , fixing the data to value 1.

4

Which book is that? Could it be referring to the old PyMC 2.x library?

5

Bayesian method for hackers. If it a change from pymc2.x to 4.0. Can you please explain.

6

@anurag2444 You might want to read the PyMC3 version, whose syntax is much closer to PyMC v4.x (current) than PyMC v2.x: GitHub - CamDavidsonPilon/Probabilistic-Programming-and-Bayesian-Methods-for-Hackers: aka "Bayesian Methods for Hackers": An introduction to Bayesian methods + probabilistic programming with a computation/understanding-first, mathematics-second point of view. All in pure Python ;)

It seems like PyMC v2.x used to have the keyword arguments observed and value, whereas in PyMC3 and PyMC v4.x we simply use observed which is either None or a value.

1 Like
7

Thanks @ricardoV94 . Will check it out.