# Homogeneity Score¶

## Module Interface¶

class torchmetrics.clustering.HomogeneityScore(**kwargs)[source]

Compute Homogeneity Score.

The homogeneity score is a metric to measure the homogeneity of a clustering. A clustering result satisfies homogeneity if all of its clusters contain only data points which are members of a single class. The metric is not symmetric, therefore swapping preds and target yields a different score.

This clustering metric is an extrinsic measure, because it requires ground truth clustering labels, which may not be available in practice since clustering in generally is used for unsupervised learning.

As input to forward and update the metric accepts the following input:

• preds (Tensor): single integer tensor with shape (N,) with predicted cluster labels

• target (Tensor): single integer tensor with shape (N,) with ground truth cluster labels

As output of forward and compute the metric returns the following output:

• rand_score (Tensor): A tensor with the Rand Score

Parameters:

Example

>>> import torch
>>> from torchmetrics.clustering import HomogeneityScore
>>> preds = torch.tensor([2, 1, 0, 1, 0])
>>> target = torch.tensor([0, 2, 1, 1, 0])
>>> metric = HomogeneityScore()
>>> metric(preds, target)
tensor(0.4744)
plot(val=None, ax=None)[source]

Plot a single or multiple values from the metric.

Parameters:
• val (Union[Tensor, Sequence[Tensor], None]) – Either a single result from calling metric.forward or metric.compute or a list of these results. If no value is provided, will automatically call metric.compute and plot that result.

• ax (Optional[Axes]) – An matplotlib axis object. If provided will add plot to that axis

Return type:
Returns:

Figure and Axes object

Raises:

ModuleNotFoundError – If matplotlib is not installed

>>> # Example plotting a single value
>>> import torch
>>> from torchmetrics.clustering import HomogeneityScore
>>> metric = HomogeneityScore()
>>> metric.update(torch.randint(0, 4, (10,)), torch.randint(0, 4, (10,)))
>>> fig_, ax_ = metric.plot(metric.compute())
>>> # Example plotting multiple values
>>> import torch
>>> from torchmetrics.clustering import HomogeneityScore
>>> metric = HomogeneityScore()
>>> values = [ ]
>>> for _ in range(10):
...     values.append(metric(torch.randint(0, 4, (10,)), torch.randint(0, 4, (10,))))
>>> fig_, ax_ = metric.plot(values)

## Functional Interface¶

torchmetrics.functional.clustering.homogeneity_score(preds, target)[source]

Compute the Homogeneity score between two clusterings.

Parameters:
• preds (Tensor) – predicted cluster labels

• target (Tensor) – ground truth cluster labels

Return type:

Tensor

Returns:

scalar tensor with the rand score

Example

>>> from torchmetrics.functional.clustering import homogeneity_score
>>> import torch
>>> homogeneity_score(torch.tensor([0, 0, 1, 1]), torch.tensor([1, 1, 0, 0]))
tensor(1.)
>>> homogeneity_score(torch.tensor([0, 0, 1, 2]), torch.tensor([0, 0, 1, 1]))
tensor(1.)