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njit-etd2003-081 - New Jersey Institute of Technology

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117<br />

where r and p are user-defined parameters. Parameter p controls the progressive weight<br />

that is placed on differences on individual dimensions; parameter r controls the<br />

progressive weight that is placed on larger differences between objects. If r and p are<br />

equal to 2, then this distance is equal to the Euclidian distance.<br />

3.15.9 Percent Disagreement<br />

This measure is particularly useful if the data for the dimensions included in the analysis<br />

are categorical in nature. This distance is computed as:<br />

3.15.10 Amalgamation or Linkage Rules<br />

At the first step, when each object represents its own cluster, the distances between those<br />

objects are defined by the chosen distance measure. However, once several objects have<br />

been linked together, how does one determine the distances between those new clusters<br />

In other words, one needs a linkage or amalgamation rule to determine when two<br />

clusters are sufficiently similar to be linked together. There are various possibilities: for<br />

example, one could link two clusters together when any two objects in the two clusters<br />

are closer together than the respective linkage distance. Put another way, the "nearest<br />

neighbors" across clusters were used to determine the distances between clusters; this<br />

method is called single linkage. This rule produces "stringy" types <strong>of</strong> clusters, that is,<br />

clusters "chained together" by only single objects that happen to be close together.

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