Discrete credal set

An ArrayDiscreteCredalSet represents a finite set of candidate probability distributions. Unlike a convex credal set, only the listed members are considered part of the set — no interpolation between them is implied.

This is the natural representation when you have a small collection of model predictions (e.g. from an ensemble) and want to keep each member separate.

from __future__ import annotations

import matplotlib.pyplot as plt
import numpy as np

from probly.plot import plot_credal_set
from probly.representation.credal_set.array import ArrayDiscreteCredalSet

# 2 instances, each with 3 member distributions over 3 classes.
# Shape: (instances, members, classes) = (2, 3, 3)
discrete = ArrayDiscreteCredalSet(
    array=np.array(
        [
            [[0.6, 0.3, 0.1], [0.2, 0.5, 0.3], [0.4, 0.2, 0.4]],
            [[0.1, 0.6, 0.3], [0.3, 0.4, 0.3], [0.2, 0.5, 0.3]],
        ]
    ),
)

print("Shape (batch dims):", discrete.shape)
print("Lower envelope (element-wise min across members):\n", discrete.lower())
print("Upper envelope (element-wise max across members):\n", discrete.upper())

Shape (batch dims): (2,)
Lower envelope (element-wise min across members):
 [[0.2 0.2 0.1]
 [0.1 0.4 0.3]]
Upper envelope (element-wise max across members):
 [[0.6 0.5 0.4]
 [0.3 0.6 0.3]]

On the simplex each member is shown as an individual scatter marker.

plot_credal_set(discrete, title="Discrete credal set")
plt.show()