Source code for skfolio.moments.expected_returns._ew_mu

"""Exponentially Weighted Expected Returns (Mu) Estimators."""

# Copyright (c) 2023
# Author: Hugo Delatte <delatte.hugo@gmail.com>
# License: BSD 3 clause
# Implementation derived from:
# scikit-learn, Copyright (c) 2007-2010 David Cournapeau, Fabian Pedregosa, Olivier
# Grisel Licensed under BSD 3 clause.

import numpy.typing as npt
import pandas as pd

from skfolio.moments.expected_returns._base import BaseMu


[docs] class EWMu(BaseMu): r"""Exponentially Weighted Expected Returns (Mu) estimator. Estimates the expected returns with the exponentially weighted mean (EWM). Parameters ---------- window_size : int, optional Window size. The model is fitted on the last `window_size` observations. The default (`None`) is to use all the data. alpha : float, default=0.2 Exponential smoothing factor. The default value is `0.2`. :math:`0 < \alpha \leq 1`. Attributes ---------- mu_ : ndarray of shape (n_assets,) Estimated expected returns of the assets. n_features_in_ : int Number of assets seen during `fit`. feature_names_in_ : ndarray of shape (`n_features_in_`,) Names of assets seen during `fit`. Defined only when `X` has assets names that are all strings. """ def __init__(self, window_size: int | None = None, alpha: float = 0.2): self.window_size = window_size self.alpha = alpha
[docs] def fit(self, X: npt.ArrayLike, y=None) -> "EWMu": """Fit the EWMu estimator model. Parameters ---------- X : array-like of shape (n_observations, n_assets) Price returns of the assets. y : Ignored Not used, present for API consistency by convention. Returns ------- self : EWMu Fitted estimator. """ X = self._validate_data(X) if self.window_size is not None: X = X[-self.window_size :] self.mu_ = pd.DataFrame(X).ewm(alpha=self.alpha).mean().iloc[-1, :].to_numpy() return self