app.py

import math
import operator as op
import itertools as it
import functools as ft
import collections as cl
from pathlib import Path

import pandas as pd
import gradio as gr
import seaborn as sns
from datasets import load_dataset
from scipy.special import expit

HDI = cl.namedtuple('HDI', 'lower, upper')

#
# See https://cran.r-project.org/package=HDInterval
#
def hdi(values, ci=0.95):
    values = sorted(filter(math.isfinite, values))
    if not values:
        raise ValueError('Empty data set')

    n = len(values)
    exclude = n - math.floor(n * ci)

    left = it.islice(values, exclude)
    right = it.islice(values, n - exclude, None)

    diffs = ((x, y, y - x) for (x, y) in zip(left, right))
    (*args, _) = min(diffs, key=op.itemgetter(-1))

    return HDI(*args)

#
#
#
def load(repo):
    parameter = 'parameter'
    items = [
        'chain',
        'sample',
        parameter,
        'model',
        'value',
    ]
    dataset = load_dataset(repo)

    return (dataset
            .get('train')
            .to_pandas()
            .filter(items=items)
            .query(f'{parameter} == "alpha"')
            .drop(columns=parameter))

def summarize(df, ci=0.95):
    def _aggregate(i, g):
        values = g['value']
        interval = hdi(values, ci)

        agg = {
            'model': i,
            'ability': values.median(),
            'uncertainty': interval.upper - interval.lower,
        }
        agg.update(interval._asdict())

        return agg

    groups = df.groupby('model', sort=False)
    records = it.starmap(_aggregate, groups)

    return pd.DataFrame.from_records(records)

def rank(df, ascending, name='rank'):
    df = (df
          .sort_values(by=['ability',  'uncertainty'],
                       ascending=[ascending, not ascending])
          .drop(columns='uncertainty')
          .reset_index(drop=True))
    df.index += 1

    return df.reset_index(names=name)

def compare(df, model_1, model_2):
    mcol = 'model'
    models = [
        model_1,
        model_2,
    ]
    view = (df
            .query(f'{mcol} in @models')
            .pivot(index=['chain', 'sample'],
                   columns=mcol,
                   values='value'))

    return expit(view[model_1] - view[model_2])

#
#
#
class DataPlotter:
    def __init__(self, df):
        self.df = df

    def plot(self):
        ax = self.draw()
        ax.grid(visible=True,
                axis='both',
                alpha=0.25,
                linestyle='dotted')

        fig = ax.get_figure()
        fig.tight_layout()

        return fig

    def draw(self):
        raise NotImplementedError()

class RankPlotter(DataPlotter):
    _y = 'y'

    @ft.cached_property
    def y(self):
        return self.df[self._y]

    def __init__(self, df, top=10):
        view = rank(summarize(df), True, self._y)
        view = (view
                .tail(top)
                .sort_values(by=self._y, ascending=False))
        super().__init__(view)

    def draw(self):
        ax = self.df.plot.scatter('ability', self._y)
        ax.hlines(self.y,
                  xmin=self.df['lower'],
                  xmax=self.df['upper'],
                  alpha=0.5)
        ax.set_ylabel('')
        ax.set_yticks(self.y, self.df['model'])

        return ax

class ComparisonPlotter(DataPlotter):
    def __init__(self, df, model_1, model_2, ci=0.95):
        super().__init__(compare(df, model_1, model_2))
        self.interval = hdi(self.df, ci)

    def draw(self):
        ax = sns.ecdfplot(self.df)

        (_, color, *_) = sns.color_palette()
        ax.axvline(x=self.df.median(),
                   color=color,
                   linestyle='dashed')
        ax.axvspan(xmin=self.interval.lower,
                   xmax=self.interval.upper,
                   alpha=0.15,
                   color=color)
        ax.set_xlabel('Pr(M$_{1}$ \u003E M$_{2}$)')

        return ax

def cplot(df, ci=0.95):
    def _plot(model_1, model_2):
        cp = ComparisonPlotter(df, model_1, model_2, ci)
        return cp.plot()

    return _plot

def display(name, prefix='_'):
    path = Path(f'{prefix}{name.upper()')
    return (path
            .with_suffix('.md')
            .read_text())


#
#
#
with gr.Blocks() as demo:
    df = load('jerome-white/alpaca-bt-stan')

    gr.Markdown('# Alpaca Bradley–Terry')
    with gr.Row():
        with gr.Column():
            gr.Markdown(display('readme'))

        with gr.Column():
            plotter = RankPlotter(df)
            gr.Plot(plotter.plot())

    with gr.Row():
        view = rank(summarize(df), False)
        columns = { x: f'HDI {x}' for x in HDI._fields }
        for i in view.columns:
            columns.setdefault(i, i.title())
        view = (view
                .rename(columns=columns)
                .style.format(precision=4))

        gr.Dataframe(view)

    with gr.Row():
        with gr.Column(scale=3):
            display = gr.Plot()

        with gr.Row():
            with gr.Column():
                gr.Markdown('''

                Probability that Model 1 is preferred to Model 2. The
                solid blue curve is a CDF of that distribution;
                formally the inverse logit of the difference in model
                abilities. The dashed orange vertical line is the
                median, while the band surrounding it is its 95%
                [highest density
                interval](https://cran.r-project.org/package=HDInterval).

                ''')
            with gr.Column():
                models = sorted(df['model'].unique(), key=lambda x: x.lower())
                drops = ft.partial(gr.Dropdown, choices=models)
                inputs = [ drops(label=f'Model {x}') for x in range(1, 3) ]

                button = gr.Button(value='Compare!')
                button.click(cplot(df), inputs=inputs, outputs=[display])

    with gr.Accordion('Disclaimer', open=False):
        gr.Markdown(display('disclaimer'))

demo.launch()