Source code for mafese.utils.encoder

#!/usr/bin/env python
# Created by "Thieu" at 13:58, 09/05/2023 ----------%                                                                               
#       Email: nguyenthieu2102@gmail.com            %                                                    
#       Github: https://github.com/thieu1995        %                         
# --------------------------------------------------%

import numpy as np


class LabelEncoder:
    """
    Encode categorical features as integer labels.
    """

    def __init__(self):
        self.unique_labels = None
        self.label_to_index = {}

    def fit(self, y):
        """
        Fit label encoder to a given set of labels.

        Parameters:
        -----------
        y : array-like
            Labels to encode.
        """
        self.unique_labels = np.unique(y)
        self.label_to_index = {label: i for i, label in enumerate(self.unique_labels)}

    def transform(self, y):
        """
        Transform labels to encoded integer labels.

        Parameters:
        -----------
        y : array-like
            Labels to encode.

        Returns:
        --------
        encoded_labels : array-like
            Encoded integer labels.
        """
        if self.unique_labels is None:
            raise ValueError("Label encoder has not been fit yet.")
        return np.array([self.label_to_index[label] for label in y])

    def fit_transform(self, y):
        """Fit label encoder and return encoded labels.

        Parameters
        ----------
        y : array-like of shape (n_samples,)
            Target values.

        Returns
        -------
        y : array-like of shape (n_samples,)
            Encoded labels.
        """
        self.fit(y)
        return self.transform(y)

    def inverse_transform(self, y):
        """
        Transform integer labels to original labels.

        Parameters:
        -----------
        y : array-like
            Encoded integer labels.

        Returns:
        --------
        original_labels : array-like
            Original labels.
        """
        if self.unique_labels is None:
            raise ValueError("Label encoder has not been fit yet.")
        return np.array([self.unique_labels[i] if i in self.label_to_index.values() else "unknown" for i in y])


class ObjectiveScaler:
    """
    For label scaler in classification (binary and multiple classification)
    """
    def __init__(self, obj_name="sigmoid", ohe_scaler=None):
        """
        ohe_scaler: Need to be an instance of One-Hot-Encoder for softmax scaler (multiple classification problem)
        """
        self.obj_name = obj_name
        self.ohe_scaler = ohe_scaler

    def transform(self, data):
        if self.obj_name == "sigmoid" or self.obj_name == "self":
            return data
        elif self.obj_name == "hinge":
            data = np.squeeze(np.array(data))
            data[np.where(data == 0)] = -1
            return data
        elif self.obj_name == "softmax":
            data = self.ohe_scaler.fit_transform(np.reshape(data, (-1, 1)))
            return data

    def inverse_transform(self, data):
        if self.obj_name == "sigmoid":
            data = np.squeeze(np.array(data))
            data = np.rint(data).astype(int)
        elif self.obj_name == "hinge":
            data = np.squeeze(np.array(data))
            data = np.ceil(data).astype(int)
            data[np.where(data == -1)] = 0
        elif self.obj_name == "softmax":
            data = np.squeeze(np.array(data))
            data = np.argmax(data, axis=1)
        return data