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  2. Database index - Wikipedia

    en.wikipedia.org/wiki/Database_index

    This may improve the joins of these tables on the cluster key, since the matching records are stored together and less I/O is required to locate them. [2] The cluster configuration defines the data layout in the tables that are parts of the cluster. A cluster can be keyed with a B-tree index or a hash table. The data block where the table ...

  3. Cluster analysis - Wikipedia

    en.wikipedia.org/wiki/Cluster_analysis

    Cluster analysis or clustering is the task of grouping a set of objects in such a way that objects in the same group (called a cluster) are more similar (in some specific sense defined by the analyst) to each other than to those in other groups (clusters).

  4. Automatic clustering algorithms - Wikipedia

    en.wikipedia.org/wiki/Automatic_Clustering...

    Automatic clustering algorithms are algorithms that can perform clustering without prior knowledge of data sets. In contrast with other cluster analysis techniques, automatic clustering algorithms can determine the optimal number of clusters even in the presence of noise and outlier points. [1] [needs context]

  5. Determining the number of clusters in a data set - Wikipedia

    en.wikipedia.org/wiki/Determining_the_number_of...

    When clustering text databases with the cover coefficient on a document collection defined by a document by term D matrix (of size m×n, where m is the number of documents and n is the number of terms), the number of clusters can roughly be estimated by the formula where t is the number of non-zero entries in D. Note that in D each row and each ...

  6. Model-based clustering - Wikipedia

    en.wikipedia.org/wiki/Model-based_clustering

    Model-based clustering was first invented in 1950 by Paul Lazarsfeld for clustering multivariate discrete data, in the form of the latent class model. [ 41 ] In 1959, Lazarsfeld gave a lecture on latent structure analysis at the University of California-Berkeley, where John H. Wolfe was an M.A. student.

  7. 80 of the Most Useful Excel Shortcuts - AOL

    www.aol.com/lifestyle/80-most-useful-excel...

    These shortcuts, also called hotkeys, consist of two or more keys pressed at the same time. Here are some of the most useful Excel hotkeys to make a wide range of spreadsheet tasks easier.

  8. Biclustering - Wikipedia

    en.wikipedia.org/wiki/Biclustering

    Biclustering, block clustering, [1] [2] Co-clustering or two-mode clustering [3] [4] [5] is a data mining technique which allows simultaneous clustering of the rows and columns of a matrix. The term was first introduced by Boris Mirkin [ 6 ] to name a technique introduced many years earlier, [ 6 ] in 1972, by John A. Hartigan .

  9. Correlation clustering - Wikipedia

    en.wikipedia.org/wiki/Correlation_clustering

    The minimum disagreement correlation clustering problem is the following optimization problem: + + (). Here, the set + contains the attractive edges whose endpoints are in different components with respect to the clustering and the set () contains the repulsive edges whose endpoints are in the same component with respect to the clustering .