| 释义 |
ultrametric, a. and n. Math.|ʌltrəˈmɛtrɪk|
[f. ultra- + metric a.1 and n.1]
A. adj. Of a metric: satisfying the ultrametric inequality, which states that the distance between two points as defined by this metric must be less than or equal to the greater of the two distances between either of these points and any third point; of or pertaining to such a metric.
B. n. A metric which satisfies this inequality.
1967J. A. Hartigan in Jrnl. Amer. Statistical Assoc. LXII. 1141 Johnson..considers the idea of a distance function satisfying the ‘ultrametric’ inequality, which is equivalent to a similarity matrix with exact structure. 1967Math. Biosciences I. 175 A 1-metric space is usually called a metric space and a 0-metric space an ultrametric space. 1972Computer Jrnl. XV. 212/1 The only consistent difference is between the ultrametric data-sets D, E, and F versus the non-ultrametric sets A, B, and C, with the ultrametrics faring somewhat better on the whole. 1974P. H. A. Sneath in Carlile & Skehel Evolution in Microbial World 18 It can be seen that the number of PAM units from the root to any tip is about sixty-five, a fairly good ultrametric. 1988Literary & Linguistic Computing III. 125/1 The tree representation model most widely applied to the structuring of large bodies of data is based on the use of ultrametric trees or dendrograms. Ibid. The ultrametric model has some advantages. |