QQ plots in Arviz

Lime · April 11, 2021, 10:43pm

Does Arviz provide an equivalent to the ppc_loo_pit_qq function in Bayesplot? Does it provide any kind of qq-plot capability for plotting observations against the posterior predictive at all?

jonsedar · April 11, 2021, 10:47pm

Per the docs, this might serve your purpose: arviz.plot_loo_pit — ArviZ dev documentation

EDIT, ah, you’re after a QQ plot in particular… I imagine this isn’t too hard to create

Lime · April 11, 2021, 10:54pm

Hi Jon – I’m aware of the plot_loo_pit function, but I don’t see any. I’m interested in whether Arviz has any way to draw qq-plots, or whether I have to use a function from another package or build one myself.

jonsedar · April 11, 2021, 11:06pm

I haven’t looked properly at the Arviz code before, but in my unqualified opinion it looks pretty good. Should be reasonably straightforward to create a new partner function to arviz/plots/loopitplot.py and I bet it would be well received as a contribution!

github.com

arviz-devs/arviz/blob/main/arviz/plots/loopitplot.py

"""Plot LOO-PIT predictive checks of inference data."""
import numpy as np
import scipy.stats as stats

from ..labels import BaseLabeller
from ..rcparams import rcParams
from ..stats import loo_pit as _loo_pit
from ..stats.density_utils import kde
from .plot_utils import get_plotting_function


def plot_loo_pit(
    idata=None,
    y=None,
    y_hat=None,
    log_weights=None,
    ecdf=False,
    ecdf_fill=True,
    n_unif=100,
    use_hdi=False,

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OriolAbril · April 12, 2021, 2:35am

It would definitely be well received, and it should not require many changes as it’s mostly skipping some steps in the loo-pit ECDF diff plot which is already implemented.

jonsedar · April 12, 2021, 5:35am

I figured most of the required infra would be there I should have time to breathe in a couple of weeks so will try then if no one else wants to

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QQ plots in Arviz

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