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  • Articles  (8)
  • Articles: DFG German National Licenses  (8)
  • Latest Papers from Table of Contents or Articles in Press
  • cluster analysis  (8)
  • Springer  (8)
  • American Geophysical Union (AGU)
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  • 1980-1984  (8)
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  • Geosciences  (8)
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  • Articles  (8)
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  • Articles: DFG German National Licenses  (8)
  • Latest Papers from Table of Contents or Articles in Press
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  • Springer  (8)
  • American Geophysical Union (AGU)
  • Annual Reviews
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Mathematical geology 14 (1982), S. 405-417 
    ISSN: 1573-8868
    Keywords: Markov Chain ; carbonate sequences ; cluster analysis ; substitutability analysis ; entropy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract It is difficult to develop stochastic models for complex lithological sequences that are typically associated with intertidal-supratidal depositional environments. A sequence from the Upper Silurian Leopold Formation on eastern Somerset Island is used to demonstrate that a combination of cluster analysis, Markov Chain analysis, and substitutability analysis can give considerable insight into the nature of such complex successions. The high variability of this sequence was created by a combination of (a) variation in the depositional environment, (b) variation in the degree of dolomitization, (c) variation in the clastic influx, (d) random highenergy (possibly storm associated events) and (e) random breaks in the succession of depositional environments.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Mathematical geology 14 (1982), S. 661-667 
    ISSN: 1573-8868
    Keywords: biotopes ; Bray-Curtis ; cluster analysis ; foraminifera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Transformation of data effectively limits the distortion by outlying values on the Bray-Curtis similarity measure. It represents an effective method of using cluster analysis in distinguishing biotopes of benthic foraminifera.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Mathematical geology 16 (1984), S. 139-153 
    ISSN: 1573-8868
    Keywords: cluster analysis ; numerical taxonomy ; natural classification ; multimodality ; density estimation ; orientation data ; fabric diagrams
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract An algorithm to classify data points on the sphere in distinct cluster groups is defined. The characteristics of the cluster groups and the rule for assigning data to the groups are related to a continuous differentiable density estimation. The modes of the estimated density are assumed to be representative of the groups; data points are then assigned to the mode reached by the steepest ascent. The major advantage of this procedure is its sensitivity in detecting cluster groups independently of their geometry and configuration. As a consequence, the procedure is capable of handling orientation data that may be arranged in girdles.
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  • 4
    ISSN: 1573-8868
    Keywords: aerial radiometrics ; cluster analysis ; k-means analysis ; principal components analysis ; Copper Mountain ; Wyoming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract One objective of the aerial radiometric surveys flown as part of the U.S. Department of Energy's National Uranium Resource Evaluation (NURE) program was to ascertain the spatial distribution of near-surface radioelement abundances on a regional scale. Some method for identifying groups of observations with similar γ-ray spectral signatures and radioelement concentration values was therefore required. It is shown in this paper that cluster analysis can identify such groups with or without a priori knowledge of the geology of an area. An approach that combines principal components analysis with convergentk-means cluster analysis is used to classify 6991 observations (each observation comprising three radiometric variables) from the Precambrian rocks of the Copper Mountain, Wyoming area. This method is compared with a convergentk-means analysis that utilizes available geologic knowledge. Both methods identify four clusters. Three of the clusters represent background values for the Precambrian rocks of the area, and the fourth represents outliers (anomalously high214Bi). A segmentation of the data corresponding to “geologic reality” as interpreted by other methods has been achieved by perceptive quantitative analysis of aerial radiometric data. The techniques employed are composites of classical clustering methods designed to handle the special problems presented by large data sets.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Mathematical geology 13 (1981), S. 225-235 
    ISSN: 1573-8868
    Keywords: multivariate analysis ; cluster analysis ; structural distortion ; minimum spanning tree ; Silurian Tonoloway Limestone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Cluster analysis groups samples, but does not generally show gradations between clusters. To illustrate these relationships, principal-coordinate analysis and multidimensional scaling can be employed, but these methods may not be appropriate due to structural distortion. A minimum spanning tree (MST) computes a point-to-point path through the original matrix, and clusters are mapped on the MST diagram. The MST linkages, therefore, provide a natural continuum between the clusters, without distortion. Forty-six Silurian Tonoloway Limestone samples were analyzed for 16 sedimentary features indicative of subaerial exposure. Cluster analysis identified nine clusters which were reduced to five final, ordered groups by MST.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Mathematical geology 14 (1982), S. 259-270 
    ISSN: 1573-8868
    Keywords: cluster analysis ; EXTENDED QMODEL ; filtering ; fuzzyc-means ; fuzzy sets ; linear unmixing ; QMODEL ; shape analysis ; substructure analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Many data sets can be viewed as a collection of samples representing mixtures of a relatively small number of end members. When end members are present in the sample set, the algorithm QMODEL by Klovan and Miesch can efficiently determine proportionate contributions. EXTENDED QMODEL by Full, Ehrlich, and Klovan was designed to deduce the composition of realistic end members when the end members are not represented by samples. However, in the presence of high levels of random variation or outliers not belonging to the system of interest, EXTENDED QMODEL may not be reliable inasmuch as it is largely dependent on extreme values for definition of an initial mixing polyhedron. FUZZY QMODEL utilizes the fuzzy c-means algorithm of Bezdek to provide an alternative initial mixing polyhedron. This algorithm utilizes the collective property of all the data rather than outliers and so can produce suitable solutions in the presence of noisy or “messy” data points.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Mathematical geology 16 (1984), S. 283-301 
    ISSN: 1573-8868
    Keywords: Bayesian classifiers ; classification ; cluster analysis ; cluster validity ; fuzzyc means ; fuzzyc varieties ; fuzzy covariances ; geochemical prospecting ; glacial till ; kriging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract To evaluate the provenance of glacial till, the trace element content of magnetite was used. Magnetite was present in all known rock types and all till samples in the area investigated. By using fuzzy-set theory it was possible to group samples of magnetite taken from bedrock into relatively homogeneous and geologically meaningful groups and also, by fuzzy classification, to relate the till samples to the rocks in such a way that the relative contribution of each rock type to the till is estimated. Each rock and till sample is assigned a membership value between 0 and 1 for each rock type. The membership values, for a certain rock type in the till, are then interpolated by kriging onto maps. Magnetites from skarns associated with sulfide ores especially are rather distinct, and so a map of such membership values for till unveils all known ore deposits some 1–5 km “downstream”in the general direction of the ice flow. Other anomalies show up which cannot be related to hitherto known ores or mineralizations.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Mathematical geology 16 (1984), S. 393-406 
    ISSN: 1573-8868
    Keywords: geophysical logs ; multivariate statistics ; cluster analysis ; linear programming ; dynamic programming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract The borehole slotting method previously proposed by Gordon and Reyment for two boreholes may be extended to three or more boreholes, but soon becomes computationally intractable. We propose another method based on the mixture model of cluster analysis, the computational labor of which increases linearly with the number of boreholes. This method produces profiles of the unknown strata to which the individual boreholes are easily matched by the two-borehole slotting method.
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