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CPHMM

Python implementation of Conformal Prediction for Hidden Markov Models (CP-HMM) [1].

Installation

In your chosen virtualenv (otherwise you're recommended to add "--user" as an argument to setup.py, for a local installation):

pip install -r requirements.txt
python setup.py install

Basic usage

cphmm makes use of nonconformist for Conformal Prediction. Refer to its docs for details about nonconformity measures.

import numpy as np
from cphmm.cphmm import CPHMM
from sklearn.neighbors import KNeighborsClassifier
from nonconformist.nc import ClassifierNc, ClassifierAdapter

# X: the observed states (emissions).
# Each row is an observed sequence.
# Emissions can be floats.
# NOTE: it is possible to have sequences of differents
# lengths, but you need to specify `lengths` when
# `fit()`-ing the `CPHMM` below.
X = np.array([[0, 3, 2], [4, 3, 2]])
# H: the corresponding hidden states.
# Each row is an observed sequence.
H = np.array([[0, 2, 1], [0, 0, 2]])

# Define nonconformity measure for CP
knn = KNeighborsClassifier(n_neighbors=3)
ncm = ClassifierNc(ClassifierAdapter(knn))
# Instantiate and train CP-HMM
cphmm = CPHMM(ncm, n_states=3)
cphmm.fit(X, H)

# We predict candidate hidden state sequences for
# a test object.
x_test = np.array([1, 2, 3])
# Significance level (i.e., the probability that the
# correct sequence _will not_ be in the prediction
# set.
significance = 0.2
candidate_sequences = cphmm.predict(x_test, significance)

The prediction candidate_sequences is a list of candidate sequences (tuples). The probability that the correct hidden sequence (y) is not in predicted is exactly significance, thanks to the validity guarantee.

Another simple example is in examples/example.py.

If you need help or encounter any issue, please open a ticket.

Known limitations

Only Transductive Conformal Prediction (CP) is implemented. Inductive CP may be supported in the future.

References

[1] "Hidden Markov Models with Confidence" (Giovanni Cherubin and Ilia Nouretdinov, 2016)

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Conformal Prediction for Hidden Markov Models

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