نتایج جستجو برای: compositional data

تعداد نتایج: 2424312  

2015
BERTA FERRER-ROSELL ESTHER MARTÍNEZ-GARCIA Luis Nicolau

The reduction in transportation costs when travelling with a low-cost airline (LCA) seems to have modified the composition of the trip budget. An understanding of expenditure composition when comparing LCA and legacy airline travellers is vital for destination marketers. Using micro official statistics data for air travellers to Spain in 2010 and the compositional data analysis (CODA) methodolo...

2009
R. L. Korotev R. A. Zeigler

Compositionally and petrologically, Dhofar 961, a glassy-matrix regolith breccia, is unique among lunar meteorites (Fig. 1) and distinct from any Apollo sample. In a recent paper [1], we make two observations. (1) If the ~65 known lunar meteorites represent even as few as only 30 source craters on the Moon, then there is still an 80% chance that at least one is from the South PoleAitken basin. ...

2003
Edward Wolff Maria Grazia Pittau Roberto Zelli M. Grazia Pittau

Using kernel density estimation and mixture models, household size-adjusted income distributions in Italy are cross-sectionally examined over the period 1987-2000. Nonparametric tests assess the shape time invariance and the presence of modes in the distributions. Evidence shows that income tend to cluster around more than one point, giving good reasons to model the shapes by a finite mixture d...

2002
John Knight

This account gives new data on the composition of gold from various lodes and placers in southwestern British Columbia. This research is a continuation of work reported in a 1986 paper (Knight and McTaggart, 1986). This account repeats some of the introductory material of the earlier paper in order to clarify the present report. A main objective of this work is to characterize gold by its suite...

2013
Paul K. Byrne Christian Klimczak David A. Williams Debra M. Hurwitz Sean C. Solomon James W. Head Frank Preusker Jürgen Oberst

[1] In contrast to other terrestrial planets, Mercury does not possess a great variety of volcanic features, its history of volcanism instead largely manifest by expansive smooth plains. However, a set of landforms at high northern latitudes on Mercury resembles surface flow features documented on Earth, the Moon, Mars, and Venus. The most striking of such landforms are broad channels that host...

2000
Travis Pickering Shawn S. Murray Margaret J. Schoeninger Henry T. Bunn Travis R. Pickering Judith A. Marlett

We report compositional data for several foods that comprise the annual diet among Hadza foragers near Lake Eyasi in northern Tanzania. Samples collected during daily gathering trips over three "eldwork seasons were prepared according to Hadza methods. All three types of honey show moisture and starch levels similar to United States' honeys but higher levels of protein, fat, and ash. Several sa...

2007
P. Filzmoser K. Hron Peter Filzmoser Karel Hron

Outlier detection based on the Mahalanobis distance (MD) requires an appropriate transformation in case of compositional data. For the family of logratio transformations (additive, centered and isometric logratio transformation) it is shown that the MDs based on classical estimates are invariant to these transformations, and that the MDs based on affine equivariant estimators of location and co...

2007
Nicholas J. Cox

Abstract. A variety of graphs have been devised for categorical and compositional data, ranging from widely familiar to more unusual displays. Both official Stata commands and user-written programs are available. After a stacking trick for binary responses is explained, bar charts and related displays for cross-tabulations are discussed in detail. Tips and tricks are introduced for plotting cum...

2017
Gregory B. Gloor Jean M. Macklaim Vera Pawlowsky-Glahn Juan J. Egozcue

Datasets collected by high-throughput sequencing (HTS) of 16S rRNA gene amplimers, metagenomes or metatranscriptomes are commonplace and being used to study human disease states, ecological differences between sites, and the built environment. There is increasing awareness that microbiome datasets generated by HTS are compositional because they have an arbitrary total imposed by the instrument....

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