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Egozcue, J. J.; Pawlowsky‐Glahn, Vera; Figueras, Glòria Mateu; Barceló‐Vidal, C.

doi:10.1023/a:1023818214614

Cited by 1,459 publications

(342 citation statements)

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“…Several alternative log-ratio transforms of compositional data have been developed; the additive-log-ratio (alr) and the centred-log-ratio (clr) were defined by Aitchison (1986), but alr and clr transformed data are subject to restrictions in their treatment by standard methods. Isometric-log-ratio (ilr) transformed data (Egozcue et al 2003 and see Egozcue and Pawlowsky-Glahn 2006, for an introduction) can be analysed directly using standard univariate or multivariate statistical methods and this approach is used in the analysis presented here. Balances are a particular form of ilr coordinates (Egozcue and Pawlowsky-Glahn 2005) and they represent the relative variation in two groups of parts.…”

Section: Computing Log-ratiosmentioning

confidence: 99%

Spatial scale and small area population statistics for England and Wales

Lloyd

2015

International Journal of Geographical Information Science

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It is well-known that the results of analyses of aggregate data, such as those provided as outputs from censuses, are dependent on the size and shape of the zones used to report the data. However, many users of aggregate census data do not consider how far the zones utilised in their analyses capture spatial information about the population sub-groups they are studying. In addition, future data collection strategies should account for such issues. This article takes as its focus England and Wales, and it seeks to assess how far output areas (OAs) and aggregations of OAs capture information in selected population sub-groups and, therefore, how important it might be to use zones of a particular size in order to properly analyse the geographies of these subgroups. The article uses the index of dissimilarity, D xy (for groups x and y), and variograms to assess spatial variation in population sub-groups as represented by counts for OAs, lower layer super output areas (LSOAs), middle layer super output areas (MSOAs) and local authority districts (LAs), all produced as outputs from the Census in England and Wales. The analyses show how much information is contained at each spatial scale for sub-categories relating to age, ethnic group, housing tenure, car or van availability, qualifications, employment, limiting long-term illness (LLTI) and National Statistics Socio-economic Classification (NS-SeC). The amount of variation contained by each level of the hierarchy of zones differs markedly by population sub-group. LAs capture most (83%) of the variation in the spread of the population by the binary categorisation of White/Black, Asian and Minority Ethnic (far more than for any other variable), but there remains considerable local variation. The results suggest that zones larger than OAs are not geographically detailed enough to enable meaningful analysis of local-level differences between places and thus any alternative to the Census in the United Kingdom (with England and Wales as a specific case) must provide zones equivalent in size to OAs. If estimates are available only for larger areas then much information will be lost and our ability to explore how sub-group characteristics, or the relationships between variables, differ between localities will be considerably diminished. The results also provide evidence on some of the ways in which the population of England and Wales was geographically distributed in 2011.ARTICLE HISTORY

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Section: Computing Log-ratiosmentioning

confidence: 99%

Spatial scale and small area population statistics for England and Wales

Lloyd

2015

International Journal of Geographical Information Science

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“…To transform data from their own natural sample space to the Euclidean sample space, in order to apply classical statistical methods (i.e. kriging), the isometric log-ratio (ILR) transformation (Egozcue, Pawlowsky-Glahn, Mateu-Figueras, & Barceló-Vidal, 2003) was applied. The ILR transformation results in D − 1 variables, where D is the original number of variables.…”

Section: Methodsmentioning

confidence: 99%

Distribution of potentially toxic metals (As, Cu, Hg, Pb and Zn) in the topsoil of the Pannonian Basin System and associated parts of the surrounding orogens

Ivanišević

Malvić

2015

Journal of Maps

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The Pannonian Basin System (PBS) and associated parts of the surrounding orogens (SOs) were selected for a regional geochemical mapping of concentrations of potentially toxic metals, with the sample media the topsoil horizon. Geochemical data form a sample space that is different from Euclidean, and therefore standard statistical methods are not applicable for such data. To apply standard statistical methods, data were transformed to Euclidean space by using a special case of an isometric log-ratio transformation for a composition consisting of two parts (the first part is the metal concentration of interest; the second part is the total concentration of all other elements in the composition). Estimations were performed using deterministic (Ordinary Kriging) and stochastic (sequential Gaussian simulations (SGS)) methods. The resulting maps provide insight into the distribution of certain metals in the PBS and associated parts of the SOs, and are intended to serve as base maps for further studies. The maps obtained with SGS provide additional information on the variability (uncertainty) of estimation.ARTICLE HISTORY

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“…Filzmoser et al (2009) considered that the isometric log ratio proposed by Egozcue et al (2003) was the most appropriate transformation technique to handle environmental compositional data statistically. Compositional data are multivariate in nature, non-overlapping, and closed to some whole such as the unit or scale of measurement (here, 100%).…”

Section: Soil Test Nmentioning

confidence: 99%

“…As a result, a soil test based on total C and N, as well as a filling value to 100% (F v = 100%-%C-%N) that amalgamates all other components such as ash, S, O, and H, would be useful to model lettuce response to added N in organic soils (Duguet et al 2006). Compositional log ratio transformations were proposed to handle data constrained to 100% (Aitchison 1986;Egozcue et al 2003).…”

Section: Introductionmentioning

confidence: 99%

Meta-analysis of lettuce (Lactuca sativaL.) response to added N in organic soils¹

Gonzalez¹,

Pellerin²,

Parent³

2016

Can. J. Plant Sci.

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A soil test N (STN) is required to implement N fertilizer recommendations for vegetable crops in cultivated organic soils. A STN can be developed using the isometric log ratio (ILR) to balance soil C, N, and other soil components amalgamated into a filling value (F v ) and to derive a Mahalanobis distance (M 2 ) as STN. Our objective was to conduct a meta-analysis of multi-year and multi-site N trials on lettuce (Latuca sativa L.) response to added N along a gradient of M 2 values, and to develop an N recommendation model. Twenty-four N fertilization experiments were conducted from 2002 to 2006 in organic soils of southwestern Quebec. Each crop received four N rates from zero to 120-150 kg N ha −1 applied before seeding or in split applications. The relationship between N requirements by lettuce and STN was quadratic whether lettuce was seeded or planted. There were three STN fertility classes delineated by M 2 values of 1 and 5.5. The N recommendation model and its uncertainty were valuable for M 2 values up to 8.4. This approach provides a reliable test soil N to implement appropriate fertilizer recommendations for lettuce in organic soils.Key words: compositional data analysis, meta-analysis, lettuce, C/N ratio, soil test N, yield response. Mots-clés : analyse compositionnelle de données, méta-analyse, laitue, rapport C/N, test de N du sol, réponse du rendement.

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Cited by 1,459 publications

References 10 publications

Spatial scale and small area population statistics for England and Wales

Spatial scale and small area population statistics for England and Wales

Distribution of potentially toxic metals (As, Cu, Hg, Pb and Zn) in the topsoil of the Pannonian Basin System and associated parts of the surrounding orogens

Meta-analysis of lettuce (Lactuca sativaL.) response to added N in organic soils¹

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Untitled

Cited by 1,459 publications

References 10 publications

Spatial scale and small area population statistics for England and Wales

Spatial scale and small area population statistics for England and Wales

Distribution of potentially toxic metals (As, Cu, Hg, Pb and Zn) in the topsoil of the Pannonian Basin System and associated parts of the surrounding orogens

Meta-analysis of lettuce (Lactuca sativaL.) response to added N in organic soils1

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Meta-analysis of lettuce (Lactuca sativaL.) response to added N in organic soils¹