AGNES

toyml.clustering.agnes.AGNES dataclass

AGNES(n_cluster: int, linkage: Literal['single', 'complete', 'average'] = 'single', distance_metric: Literal['euclidean'] = 'euclidean', distance_matrix_: list[list[float]] = list(), clusters_: list[ClusterTree] = list(), labels_: list[int] = list(), cluster_tree_: Optional[ClusterTree] = None, linkage_matrix: list[list[float]] = list(), _cluster_index: int = 0)

Agglomerative clustering algorithm (Bottom-up Hierarchical Clustering)

Examples:

>>> from toyml.clustering import AGNES
>>> dataset = [[1, 0], [1, 1], [1, 2], [10, 0], [10, 1], [10, 2]]
>>> agnes = AGNES(n_cluster=2).fit(dataset)
>>> print(agnes.labels_)
[0, 0, 0, 1, 1, 1]

>>> # Using fit_predict method
>>> labels = agnes.fit_predict(dataset)
>>> print(labels)
[0, 0, 0, 1, 1, 1]

>>> # Using different linkage methods
>>> agnes = AGNES(n_cluster=2, linkage="complete").fit(dataset)
>>> print(agnes.labels_)
[0, 0, 0, 1, 1, 1]

>>> # Plotting dendrogram
>>> agnes = AGNES(n_cluster=1).fit(dataset)
>>> agnes.plot_dendrogram(show=True)

The AGNES Dendrogram Plot

References

1. Zhou Zhihua
2. Tan

n_cluster instance-attribute

n_cluster: int

The number of clusters, specified by user.

linkage class-attribute instance-attribute

linkage: Literal['single', 'complete', 'average'] = 'single'

The linkage method to use.

distance_metric class-attribute instance-attribute

distance_metric: Literal['euclidean'] = 'euclidean'

The distance metric to use.(For now we only support euclidean).

distance_matrix_ class-attribute instance-attribute

distance_matrix_: list[list[float]] = field(default_factory=list)

The distance matrix.

clusters_ class-attribute instance-attribute

clusters_: list[ClusterTree] = field(default_factory=list)

The clusters.

labels_ class-attribute instance-attribute

labels_: list[int] = field(default_factory=list)

The labels of each sample.

fit

fit(dataset: list[list[float]]) -> AGNES

Fit the model.

Source code in toyml/clustering/agnes.py

def fit(self, dataset: list[list[float]]) -> AGNES:
    """
    Fit the model.
    """
    self._validate(dataset)
    n = len(dataset)
    self.clusters_ = [ClusterTree(cluster_index=i, sample_indices=[i]) for i in range(n)]
    self._cluster_index = n
    self.distance_matrix_ = self._get_init_distance_matrix(dataset)
    while len(self.clusters_) > self.n_cluster:
        (i, j), cluster_ij_distance = self._get_closest_clusters()
        # merge cluster_i and cluster_j
        self._merge_clusters(i, j, cluster_ij_distance)
        # update distance matrix
        self._update_distance_matrix(dataset, i, j)
    # build cluster_tree_
    self.cluster_tree_ = self._build_cluster_tree(n)
    # assign dataset labels
    self._get_labels(len(dataset))
    return self

fit_predict

fit_predict(dataset: list[list[float]]) -> list[int]

Fit the model and return the labels of each sample.

Source code in toyml/clustering/agnes.py

def fit_predict(self, dataset: list[list[float]]) -> list[int]:
    """
    Fit the model and return the labels of each sample.
    """
    self.fit(dataset)
    return self.labels_

plot_dendrogram

plot_dendrogram(figure_name: str = 'agnes_dendrogram.png', show: bool = False) -> None

Plot the dendrogram of the clustering result.

This method visualizes the hierarchical structure of the clustering using a dendrogram. It requires the number of clusters to be set to 1 during initialization.

PARAMETER	DESCRIPTION
figure_name	The filename for saving the plot. Defaults to "agnes_dendrogram.png". TYPE: str DEFAULT: 'agnes_dendrogram.png'
show	If True, displays the plot. Defaults to False. TYPE: bool DEFAULT: False

RAISES	DESCRIPTION
ValueError	If the number of clusters is not 1.

Note

This method requires matplotlib and scipy to be installed.

Source code in toyml/clustering/agnes.py

def plot_dendrogram(
    self,
    figure_name: str = "agnes_dendrogram.png",
    show: bool = False,
) -> None:
    """
    Plot the dendrogram of the clustering result.

    This method visualizes the hierarchical structure of the clustering
    using a dendrogram. It requires the number of clusters to be set to 1
    during initialization.

    Args:
        figure_name: The filename for saving the plot.
                           Defaults to "agnes_dendrogram.png".
        show: If True, displays the plot. Defaults to False.

    Raises:
        ValueError: If the number of clusters is not 1.

    Note:
        This method requires matplotlib and scipy to be installed.
    """
    import matplotlib.pyplot as plt
    import numpy as np

    from scipy.cluster.hierarchy import dendrogram

    if self.n_cluster != 1:
        raise ValueError("The number of clusters should be 1 to plot dendrogram")
    # Plot the dendrogram
    plt.figure(figsize=(10, 7))
    dendrogram(np.array(self.linkage_matrix))
    plt.title("AGNES Dendrogram")
    plt.xlabel("Sample Index")
    plt.ylabel("Distance")
    plt.savefig(f"{figure_name}", dpi=300, bbox_inches="tight")
    if show:
        plt.show()

toyml.clustering.agnes.ClusterTree dataclass

ClusterTree(cluster_index: int, parent: Optional[ClusterTree] = None, children: list[ClusterTree] = list(), sample_indices: list[int] = list(), children_cluster_distance: Optional[float] = None)

Represents a node in the hierarchical clustering tree.

Each node is a cluster containing sample indices. Leaf nodes represent individual samples, while internal nodes represent merged clusters. The root node contains all samples.

parent class-attribute instance-attribute

parent: Optional[ClusterTree] = None

Parent node.

children class-attribute instance-attribute

children: list[ClusterTree] = field(default_factory=list)

Children nodes.

sample_indices class-attribute instance-attribute

sample_indices: list[int] = field(default_factory=list)

The cluster: dataset sample indices.