# Correlation Clustering Task

A Correlation Clustering Task is a clustering task that requires use of cluster correlation measure.

**Context:**- It can be solved by a Correlation Clustering System (that applies a correlation clustering algorithm).

**Counter-Example(s):****See:**Clustering with Advice; Clustering with Constraints; Clustering with Qualitative Information; Clustering with Side Information, Correlation, Feature Vector, High-Dimensional Space, Cluster Analysis, Decorrelation, Clustering High-Dimensional Data.

## References

### 2015

- (Wikipedia, 2015) ⇒ http://en.wikipedia.org/wiki/correlation_clustering Retrieved:2015-11-8.
- Clustering is the problem of partitioning data points into groups based on their similarity.
**Correlation clustering**provides a method for clustering a set of objects into the optimum number of clusters without specifying that number in advance.^{[1]}

- Clustering is the problem of partitioning data points into groups based on their similarity.

- ↑ Becker, Hila, "A Survey of Correlation Clustering", 5 May 2005

- (Wikipedia, 2015) ⇒ http://en.wikipedia.org/wiki/correlation_clustering#Correlation_clustering Retrieved:2015-11-8.
**Correlation clustering**also relates to a different task, where correlations among attributes of feature vectors in a high-dimensional space are assumed to exist guiding the clustering process. These correlations may be different in different clusters, thus a global decorrelation cannot reduce this to traditional (uncorrelated) clustering.Correlations among subsets of attributes result in different spatial shapes of clusters. Hence, the similarity between cluster objects is defined by taking into account the local correlation patterns. With this notion, the term has been introduced in simultaneously with the notion discussed above. Different methods for correlation clustering of this type are discussed in, the relationship to different types of clustering is discussed in, see also Clustering high-dimensional data.

Correlation clustering (according to this definition) can be shown to be closely related to biclustering. As in biclustering, the goal is to identify groups of objects that share a correlation in some of their attributes; where the correlation is usually typical for the individual clusters.

### 2011

- (Wirth, 2011) ⇒ Anthony Wirth. (2011). “Correlation Clustering.” In: (Sammut & Webb, 2011) p.227
- QUOTE: In its rawest form, correlation clustering is graph optimization problem. Consider a clustering C to be a mapping from the elements to be clustered, V , to the set {1, …, | V | }, so that u and v are in the same cluster if and only if C[u] = C[v]. Given a collection of items in which each pair (u, v) has two weights wuv+ and wuv− , we must find a clustering C that minimizes :[math]∑C[u]=C[v]w−uv+∑C[u]≠C[v]w+uv, \ (1)[/math] or, equivalently, maximizes :[math]∑C[u]=C[v]w+uv+∑C[u]≠C[v]w−uv. \ (2)[/math] Note that although wuv+ and wuv− may be thought of as positive and negative evidence towards coassociation, the actual weights are nonnegative.

### 2006

- (Demaine et al., 2006) ⇒ Erik D. Demaine, Dotan Emanuel, Amos Fiat, and Nicole Immorlica. (2006). “Correlation Clustering in General Weighted Graphs." Theoretical Computer Science 361, no. 2

### 2004

- (Bansal et al., 2004) ⇒ Nikhil Bansal, Avrim Blum, and Shuchi Chawla. (2004). “Correlation Clustering." Machine Learning 56, no. 1-3
- ABSTRACT: We consider the following clustering problem: we have a complete graph on [math]n[/math] vertices (items), where each edge (u, v) is labeled either + or − depending on whether u and v have been deemed to be similar or different. The goal is to produce a partition of the vertices (a clustering) that agrees as much as possible with the edge labels. That is, we want a clustering that maximizes the number of + edges within clusters, plus the number of − edges between clusters (equivalently, minimizes the number of disagreements: the number of − edges inside clusters plus the number of + edges between clusters). This formulation is motivated from a document clustering problem in which one has a pairwise similarity function f learned from past data, and the goal is to partition the current set of documents in a way that correlates with f as much as possible; it can also be viewed as a kind of “agnostic learning” problem.
An interesting feature of this clustering formulation is that one does not need to specify the number of clusters k as a separate parameter, as in measures such as k-median or min-sum or min-max clustering. Instead, in our formulation, the optimal number of clusters could be any value between 1 and n, depending on the edge labels. We look at approximation algorithms for both minimizing disagreements and for maximizing agreements. For minimizing disagreements, we give a constant factor approximation. For maximizing agreements we give a PTAS, building on ideas of Goldreich, Goldwasser, and Ron (1998) and de la Veg (1996). We also show how to extend some of these results to graphs with edge labels in [−1, + 1], and give some results for the case of random noise.

- ABSTRACT: We consider the following clustering problem: we have a complete graph on [math]n[/math] vertices (items), where each edge (u, v) is labeled either + or − depending on whether u and v have been deemed to be similar or different. The goal is to produce a partition of the vertices (a clustering) that agrees as much as possible with the edge labels. That is, we want a clustering that maximizes the number of + edges within clusters, plus the number of − edges between clusters (equivalently, minimizes the number of disagreements: the number of − edges inside clusters plus the number of + edges between clusters). This formulation is motivated from a document clustering problem in which one has a pairwise similarity function f learned from past data, and the goal is to partition the current set of documents in a way that correlates with f as much as possible; it can also be viewed as a kind of “agnostic learning” problem.