How to Obtain Proximities
Proximities are either collected by directly judging the (dis-)similarity of pairs of objects, or they are derived from score or attribute vectors associated with each of these objects. Direct proximities typically result from similarity ratings on object pairs, from rankings, or from card-sorting tasks. The anchor stimulus method leads to conditional proximities that have a restricted comparability and require special MDS procedures. Derived proximities are, in practice, most often correlations of item scores over individuals. Since there is so much work involved in building a complete proximity matrix, it is important to know about the performance of incomplete proximity matrices (with missing data) in MDS. It turns out that MDS is quite robust against randomly distributed missing data. MDS is also robust when used with coarse proximities, e.g., dichotomous proximities.
KeywordsAttribute Vector Object Pair Direct Proximity Proximity Matrix Morse Code
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