Consulta: subjectFacets:"Autocorrelation"
Registros recuperados: 16
Data/hora: 01/06/2024 11:21:01

Management zones definition using soil chemical and physical attributes in a soybean area
Provedor de dados: 70
Autores: Bazzi,Claudio L.; Souza,Eduardo G.; Uribe-Opazo,Miguel A.; Nóbrega,Lúcia H. P.; Rocha,Davi M.
Several equipments and methodologies have been developed to make available precision agriculture, especially considering the high cost of its implantation and sampling. An interesting possibility is to define management zones aim at dividing producing areas in smaller management zones that could be treated differently, serving as a source of recommendation and analysis. Thus, this trial used physical and chemical properties of soil and yield aiming at the generation of management zones in order to identify whether they can be used as recommendation and analysis. Management zones were generated by the Fuzzy C-Means algorithm and their evaluation was performed by calculating the reduction of variance and performing means tests. The division of the area into...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Precision agriculture; Spatial variability; Fuzzy clustering; Management zones; Autocorrelation; Cross-correlation.
Ano: 2013
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162013000500007

AN INTERACTIVE SOFTWARE PACKAGE FOR VALIDATING SATELLITE DATA
Provedor de dados: 72
Autores: Muraleedharan,P.M.; Pankajakshan,T.
Earth observation satellite launched in the last three decades have made vital contributions to the understanding of the planet. The earth system consisting of land, oceans and atmosphere is linked together by a number of complicated processes. Potential of microwave sensors in studying the boundary layer dynamics of the ocean-atmosphere system is well documented. Technology has revolutionized the application of such sensors and several missions are planned to take off in near future for meeting specific objectives. Launching of such sensors need to be followed by an extensive validation campaign for providing accurate and reliable information to the users. A PC-based interactive system has been developed and presented here for validating satellite mounted...
Tipo: Journal article
Palavras-chave: Validation; Microwave sensor; Autocorrelation; Sea surface temperature; Wind speed; Columnar water vapor.
Ano: 2004
URL: http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-65382004000300018

A review of techniques for spatial modeling in geographical, conservation and landscape genetics
Provedor de dados: 74
Autores: Diniz-Filho,José Alexandre Felizola; Nabout,João Carlos; Telles,Mariana Pires de Campos; Soares,Thannya Nascimento; Rangel,Thiago Fernando L.V.B.
Most evolutionary processes occur in a spatial context and several spatial analysis techniques have been employed in an exploratory context. However, the existence of autocorrelation can also perturb significance tests when data is analyzed using standard correlation and regression techniques on modeling genetic data as a function of explanatory variables. In this case, more complex models incorporating the effects of autocorrelation must be used. Here we review those models and compared their relative performances in a simple simulation, in which spatial patterns in allele frequencies were generated by a balance between random variation within populations and spatially-structured gene flow. Notwithstanding the somewhat idiosyncratic behavior of the...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Autocorrelation; Geographical genetics; Isolation-by-distance; Landscape genetics; Spatial regression.
Ano: 2009
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572009000200001

Modeling body size evolution in Felidae under alternative phylogenetic hypotheses
Provedor de dados: 74
Autores: Diniz-Filho,José Alexandre Felizola; Nabout,João Carlos.
The use of phylogenetic comparative methods in ecological research has advanced during the last twenty years, mainly due to accurate phylogenetic reconstructions based on molecular data and computational and statistical advances. We used phylogenetic correlograms and phylogenetic eigenvector regression (PVR) to model body size evolution in 35 worldwide Felidae (Mammalia, Carnivora) species using two alternative phylogenies and published body size data. The purpose was not to contrast the phylogenetic hypotheses but to evaluate how analyses of body size evolution patterns can be affected by the phylogeny used for comparative analyses (CA). Both phylogenies produced a strong phylogenetic pattern, with closely related species having similar body sizes and the...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Autocorrelation; Body size; Felidae; Phylogenetic eigenvector regression; Phylogenies.
Ano: 2009
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572009000100026

A comparison of metrics for estimating phylogenetic signal under alternative evolutionary models
Provedor de dados: 74
Autores: Diniz-Filho,José Alexandre F.; Santos,Thiago; Rangel,Thiago Fernando; Bini,Luis Mauricio.
Several metrics have been developed for estimating phylogenetic signal in comparative data. These may be important both in guiding future studies on correlated evolution and for inferring broad-scale evolutionary and ecological processes (e.g., phylogenetic niche conservatism). Notwithstanding, the validity of some of these metrics is under debate, especially after the development of more sophisticated model-based approaches that estimate departure from particular evolutionary models (i.e., Brownian motion). Here, two of these model-based metrics (Blomberg's K-statistics and Pagel's λ) are compared with three statistical approaches [Moran's I autocorrelation coefficient, coefficients of determination from the autoregressive method (ARM), and phylogenetic...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Autocorrelation; Blomberg's K; Pagel's lambda; Autoregressive method; Moran's I; Phylogenetic eigenvector regression.
Ano: 2012
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572012000400019

Application of Moran Eigenvector Maps (MEM) to irregular sampling designs
Provedor de dados: 5
Autores: Brind'Amour, Anik; Mahevas, Stephanie; Legendre, Pierre; Bellanger, Lise.
Moran’s eigenvectors maps (MEM) are attractive mathematical objects as they are fairly simple to calculate and can be used in most studies of spatially-explicit data. There is, however, an aspect of MEM analysis that still requires some investigation: the effect of irregular sampling on their modeling performance. This study investigates empirically the behavior of MEMs under different irregularity schemes. It is focusing on simulated scenarios representing sampling designs frequently encountered in ecology. We advocate that MEMs can be computed and correctly used with data coming from irregularly designed sampling surveys, given some precautions. We suggest that when the sampling sites are equally spaced but do not cover the entire study area, the MEMs...
Tipo: Text
Palavras-chave: Autocorrelation; Irregular sampling; Sampling schemes; Spatial analyses; Statistical methods.
Ano: 2018
URL: https://archimer.ifremer.fr/doc/00444/55594/57224.pdf

Estimación del horizonte de autorrecolección espacial: el caso de las variables físico-químicas estudiadas en la Ciénaga Grande de Santa Marta, Colombia
Provedor de dados: 20
Autores: Hurtado-Tobón, L.H.; García-González, M.D.
The spatial  autocorrelation range, understood here as the minimum distance between points at which the spatial correlation becomes zero, is a very useful parameter to design samples that have as goal the study of the spatial behavior of a variable.  In this paper  the estimation  of  the autocorrelation  range by means of  the  correlograms of confidence bands  are discussed in detail, and  estimations for a set of physical-chemical  variables studied at the Ciénaga Grande de Santa Marta, Northern Colombia, are made.  The results of the application show that  for four of the variables  included in the study  (Nitrite, Nitrate, the addition of Nitrite and Nitrate, and Oxygen concentration) it is not possible to analyze their spatial behavior because the...
Tipo: Journal Contribution
Palavras-chave: Autocorrelation.
Ano: 1999
URL: http://hdl.handle.net/1834/3241

Análisis de clasificación de series temporales: el caso de la salinidad en la Ciénaga Grande de Santa Marta
Provedor de dados: 20
Autores: Giraldo-H., R.; Martínez-C., J.; Hurtado-T., L.H.; Zea, S.; Madera-R., E.R.
Se realizó una clasificación numérica de 21 estaciones de monitoreo del sistema laguno -estuarino comprendido por la Ciénaga Grande de Santa Marta y el Complejo Pajarales, de acuerdo a su similaridad en el comportamiento de la salinidad del agua. Se utilizó información quincenal comprendida entre enero de 1987 y octubre de 1991. Debido a la estructura de autocorrelación de los datos fue necesario emplear los modelos ARIMA de series de tiempo en primer lugar, y posteriormente aplicar una técnica de clasificación normal con los coeficientes de la representación infinita AR calculados para cada estación. Los resultados del análisis fueron coherentes con las hipótesis planteadas acerca de la distribución de la variable en el sistema.
Tipo: Journal Contribution
Palavras-chave: Ecology; Salinity effects; Autocorrelation; Monitoring; Coastal lagoons; Estuaries; Statistical analysis; Ecology; Monitoring; Estuaries; Statistical analysis; Coastal lagoons; Http://aims.fao.org/aos/agrovoc/c_2467; Http://aims.fao.org/aos/agrovoc/c_4911; Http://aims.fao.org/aos/agrovoc/c_2673; Http://aims.fao.org/aos/agrovoc/c_7378; Http://aims.fao.org/aos/agrovoc/c_1697.
Ano: 1995
URL: http://hdl.handle.net/1834/3813

Spatial statistical analysis and selection of genotypes in plant breeding
Provedor de dados: 86
Autores: Duarte,João Batista; Vencovsky,Roland.
The objective of this study was to evaluate the efficiency of spatial statistical analysis in the selection of genotypes in a plant breeding program and, particularly, to demonstrate the benefits of the approach when experimental observations are not spatially independent. The basic material of this study was a yield trial of soybean lines, with five check varieties (of fixed effect) and 110 test lines (of random effects), in an augmented block design. The spatial analysis used a random field linear model (RFML), with a covariance function estimated from the residuals of the analysis considering independent errors. Results showed a residual autocorrelation of significant magnitude and extension (range), which allowed a better discrimination among genotypes...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Augmented design; Mixed model; Information recovery; Autocorrelation; Correlated data; Geostatistics.
Ano: 2005
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-204X2005000200002

Estimating a Demand System with Seasonally Differenced Data
Provedor de dados: 31
Autores: Harri,   Ardian; Brorsen,   B. Wade; Muhammad,   Andrew; Anderson,   John D.
Several recent papers have used annual changes and monthly data to estimate demand systems. Such use of overlapping data introduces a moving average error term. This paper shows how to obtain consistent and asymptotically efficient estimates of a demand system using seasonally differenced data. Monte Carlo simulations and an empirical application to the estimation of the U.S. meat demand are used to compare the proposed estimator with alternative estimators. Once the correct estimator is used, there is no advantage to using overlapping data in estimating a demand system.
Tipo: Journal Article
Palavras-chave: Autocorrelation; Demand system; Monte Carlo; Overlapping data; Seasonal differences; Agribusiness; Demand and Price Analysis; Financial Economics; Research Methods/ Statistical Methods; C13; Q11; Q13.
Ano: 2010
URL: http://purl.umn.edu/90679

PARAMETRIC MODELING AND SIMULATION OF JOINT PRICE-PRODUCTION DISTRIBUTIONS UNDER NON-NORMALITY, AUTOCORRELATION AND HETEROSCEDASTICITY: A TOOL FOR ASSESSING RISK IN AGRICULTURE
Provedor de dados: 31
Autores: Ramirez,   Octavio A.
This study presents a way to parametrically model and simulate multivariate distributions under potential non-normality, autocorrelation and heteroscedasticity and illustrates its application to agricultural risk analysis. Specifically, the joint probability distribution (pdf) for West Texas irrigated cotton, corn, sorghum, and wheat production and prices is estimated and applied to evaluate the changes in the risk and returns of agricultural production in the region resulting from observed and predicted price and production trends. The estimated pdf allows for time trends on the mean and the variance and varying degrees of autocorrelation and non-normality (kurtosis and right- or left-skewness) in each of the price and production variables. It also allows...
Tipo: Journal Article
Palavras-chave: Agricultural risk analysis; Autocorrelation; Heteroscedasticity; Multivariate non-normal simulation; West Texas agriculture; Research Methods/ Statistical Methods; Risk and Uncertainty.
Ano: 2000
URL: http://purl.umn.edu/15486

Estimation and testing of fixed-effect panel-data systems
Provedor de dados: 31
Autores: Blackwell,   J. Lloyd, III.
This paper describes how to specify, estimate, and test multiple-equation, fixed-effect, panel-data equations in Stata. By specifying the system of equations as seemingly unrelated regressions, Stata panel-data procedures worked seamlessly for estimation and testing of individual variable coefficients, but additional routines using test were needed for testing of individual equations and differences between equations.
Tipo: Journal Article
Palavras-chave: Panel data; Fixed effect; Multiple equations; Seemingly unrelated regressions; Heteroskedasticity; Autocorrelation; Contemporaneous correlation; Tests of linear combinations; Research Methods/ Statistical Methods.
Ano: 2005
URL: http://purl.umn.edu/117512

The Informational Fit and Maximum Likelihood in a Pooled Cross-Country Demand System with Autocorrelation
Provedor de dados: 31
Autores: Chen,   Dongling; Seale,   James L., Jr.
We fit the Florida Model with an AR(1) error structure to pooled cross-country International Comparison Project (ICP) data of Seale, Walker, and Kim and estimate the model with the minimum information (MI) estimator.  Point estimates obtained by MI are similar in value to those obtained by Seale, Walker, and Kim with maximum likelihood (ML).  Two similar simulations but with different sample sizes are conducted to compare the relative efficiencies of MI and ML with known and unknown (MLU) covariances.  In the larger sample, the MLU is more efficient in terms of root-mean-squared errors (RMSEs) than the MI.  Noteworthy, in the small sample, the MI is more efficient in terms of RMSEs than MLU, even though MLU explicitly accounts for AR(1), whereas the MI...
Tipo: Journal Article
Palavras-chave: Autocorrelation; Cross-country demand; Maximum likelihood; Minimum information; Pooled data.
Ano: 2003
URL: http://purl.umn.edu/43294

Selecting statistical models to study the relationship between soybean yield and soil physical properties
Provedor de dados: 90
Autores: Oliveira,Marcio Paulo de; Tavares,Maria Hermínia Ferreira; Uribe-Opazo,Miguel Angel; Timm,Luis Carlos.
Statistical models allow the representation of data sets and the estimation and/or prediction of the behavior of a given variable through its interaction with the other variables involved in a phenomenon. Among other different statistical models, are the autoregressive state-space models (ARSS) and the linear regression models (LR), which allow the quantification of the relationships among soil-plant-atmosphere system variables. To compare the quality of the ARSS and LR models for the modeling of the relationships between soybean yield and soil physical properties, Akaike's Information Criterion, which provides a coefficient for the selection of the best model, was used in this study. The data sets were sampled in a Rhodic Acrudox soil, along a spatial...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Autocorrelation; Cross correlation; Linear regression; State-space model; Soil and plant properties.
Ano: 2011
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832011000100009

Temporal variability of nitrogen and phosphorus concentrations in a German catchment: water sampling implication
Provedor de dados: 91
Autores: Pott,Cristiano A.; Jadoski,Sidnei O.; Schmalz,Britta; Hörmann,Georg; Fohrer,Nicola.
Daily time series were used to verify the temporal variability and to characterize the nitrogen (N) and phosphorus (P) pollution in a 462 km² catchment of the Stör river, a typical rural lowland catchment in Germany. Also, this study aimed to identify the best sampling frequency of pollution by N and P. Total phosphorus (TP), soluble orthophosphate-phosphorus (PO4-P), particulate-phosphorus (PP), total nitrogen (TN), nitrate-nitrogen (NO3-N) ammonium-nitrogen (NH4-N) and total suspended sediment (TSS) were analysed. Daily monitoring from August 8, 2009 until August 10, 2011 was conducted with an automatic water sampler at the outlet of the catchment. The results show a seasonal variability of water quality parameters with more N and P concentration in...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Water quality; Nitrate; Phosphate; Autocorrelation; Automatic water sampler; Seasonal variability.
Ano: 2014
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-43662014000800005

A dominant height growth and site index model for Pinus pseudostrobus Lindl. in northeastern Mexico
Provedor de dados: 115
Autores: Vargas-Larreta,Benedicto; Aguirre-Calderón,Oscar A.; Corral-Rivas,José J.; Crecente-Campo,Felipe; Diéguez-Aranda,Ulises.
Foresters in northeastern Mexico currently use height growth curves developed 20 years ago to estimate the dominant height and productivity of Pinus pseudostrobus Lindl. The development of new curves could improve the ability to predict heights and would allow increasingly precise yield projections for this species. Data from stem analysis of 72 P. pseudostrobus dominant trees growing in natural stands in Nuevo Leon, Tamaulipas and Coahuila (northeastern Mexico), were used to evaluate several dynamic site equations derived with the Generalized Algebraic Difference Approach (GADA). All the equations directly estimate dominant height and site index from any dominant height and age. The fittings were carried out using the base-age-invariant nested iterative...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Site quality; Height-age relationship; Generalized algebraic difference approach; Base-age dynamic equation; Autocorrelation.
Ano: 2013
URL: http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S1405-31952013000100008