A model for weak lensing

This is (Daft co-author) Hogg’s model for the observational cosmology method known as weak gravitational lensing, if that method were properly probabilistic (which it usually isn’t). Hogg put the model here for one very important reason: Because he can. Oh, and it demonstrates that you can represent non-trivial scientific projects with Daft.

import daft

pgm = daft.PGM()
pgm.add_node("Omega", r"$\Omega$", -1, 4)
pgm.add_node("gamma", r"$\gamma$", 0, 4)
pgm.add_node("obs", r"$\epsilon^{\mathrm{obs}}_n$", 1, 4, observed=True)
pgm.add_node("alpha", r"$\alpha$", 3, 4)
pgm.add_node("true", r"$\epsilon^{\mathrm{true}}_n$", 2, 4)
pgm.add_node("sigma", r"$\sigma_n$", 1, 3)
pgm.add_node("Sigma", r"$\Sigma$", 0, 3)
pgm.add_node("x", r"$x_n$", 2, 3, observed=True)
pgm.add_plate([0.5, 2.25, 2, 2.25], label=r"galaxies $n$")
pgm.add_edge("Omega", "gamma")
pgm.add_edge("gamma", "obs")
pgm.add_edge("alpha", "true")
pgm.add_edge("true", "obs")
pgm.add_edge("x", "obs")
pgm.add_edge("Sigma", "sigma")
pgm.add_edge("sigma", "obs")

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