Search results for "Regression"
showing 10 items of 2619 documents
Non-crossing quantile regression via monotone B-spline varying coefficients
2019
Quantile regression can be used to obtain a nonparametric estimate of a conditional quantile function. The presence of quantile crossing, however, leads to an invalid distribution of the response and makes it dicult to use the tted model for prediction. In this work, we show that crossing can be alleviated or completely eliminated by explicit modeling of the regression coecients as a function of the percentile values in (0,1). We illustrate the approach via a wellknown dataset by emphasizing dierences with respect to the competitors.
Explaining local governments' cost efficiency: Controllable and uncontrollable factors
2020
Abstract Efficient and effective management of public resources is essential at all levels of government. This issue has gained momentum due to the strains that affected public sector finances after the onset of the 2007/08 crisis in many countries, particularly in Europe. In this article, we evaluate the influence of environmental variables that affect local government efficiency in one European country, Spain, during the crisis years (2009–2015). To this end, and considering the possible influence of both controllable and uncontrollable factors, we use an approach that is able to analyse their impact across the conditional distribution of performance, and which controls for the (likely) e…
Analysis of the determinants of entrepreneurial intention: the case of Burkina Faso
2018
International audience; In this study, we propose to analyze students' entrepreneurial intention, drawing on Lazear's (2004) self-selection model. This model captures the role of "human capital" in employment assignment and emphasizes the importance of the variety of skills in the individual's entrepreneurial orientation. For this purpose, we have a database collected in 2017 from over 1000 students at Ouaga I and Ouaga II universities in Burkina Faso. The results of estimates obtained using the quantile regression method show a positive and significant effect of the diversity of skills on the intention score, mainly at the median level. Even if the effect is not strong, this result support…
Determinants of the interannual relationships between remote sensed photosynthetic activity and rainfall in tropical Africa
2007
International audience; The response of photosynthetic activity to interannual rainfall variations in Africa South of the Sahara is examined using 20 years (1981-2000) of Normalised Difference Vegetation Index (NDVI) AVHRR data. Linear correlations and regressions were computed between annual NDVI and annual rainfall at a 0.5° latitude/longitude resolution, based on two gridded precipitation datasets (Climate Prediction Center Merged Analysis of Precipitation [CMAP] and Climatic Research Unit [CRU]). The spatial patterns were then examined to detect how they relate to the mean annual rainfall amounts, land-cover types as from the Global Land Cover 2000 data set, soil properties and soil typ…
Application of selected methods of black box for modelling the settleability process in wastewater treatment plant
2017
The paper described how the results of measurement s of inflow wastewater temperature in the chamber, a degree of external and internal recirculation in the biological-mechanical wastewater treatment plan t (WWTP) in Cedzyna near Kielce, Poland, were used to make predictions of settleability of activated sludge. Three methods,namely: multivariate adaptive regression splines (MARS), random forests (RF) and modified random forests (RF+ SOM) were employed to compute activated sludge settleability. The results of analysis indicate that modified random forests demonstrate the best predictive abilities.
Literacy, Age and Recentness of Education Among Nordic Adults
2017
The purpose of the present study was to examine the relationship between reading literacy and age in an adult population aged 25 to 65 in Nordic countries using PIAAC 2012 data. More specifically, the study examined to what extent variations in the literacy proficiency of adults are explained by age and the recentness of qualifications when variables related to education, occupation, and skill use are controlled. The statistical method was regression analysis. The recentness of education explained only a part of the performance gap between the oldest adults and others. The significance of the length and scope of initial education in developing literacy proficiency overall, is difficult to c…
Measuring, comparing and interpreting phenotypic selection on floral scent
2022
Natural selection on floral scent composition is a key element of the hypothesis that pollinators and other floral visitors drive scent evolution. The measure of such selection is complicated by the high-dimensional nature of floral scent data and uncertainty about the cognitive processes involved in scent-mediated communication. We use dimension reduction through reduced-rank regression to jointly estimate a scent composite trait under selection and the strength of selection acting on this trait. To assess and compare variation in selection on scent across species, time and space, we reanalyse 22 datasets on six species from four previous studies. The results agreed qualitatively with prev…
Interlinkages between operational conditions and direct and indirect greenhouse gas emissions in a moving bed membrane biofilm reactor
2016
Nitrous oxide (N2O) can be emitted during wastewater treatment contributing to the global warming due to its high global warming potential,. During the last ten years, several efforts have been provided to improve knowledge on: key mechanisms, operating factors and influent features affecting the N2O production/emission. However, the knowledge on the investigated issues is not completely mature. Indeed, in terms of mathematical modelling, literature shows that a reliable model has not yet been established due to the huge data set required and the complexity of the mechanistic models indicated as the most accurate. In this work, the first attempt to perform a multiregression analysis is pres…
Adaptive smoothing spline using non-convex penalties
2022
We propose a new adaptive penalty for smoothing via penalized splines. The new form of adaptive penalization is based on penalizing the differences of the coefficients of adjacent bases, using non-convex penalties. This makes possible to estimate curves with varying amounts of smoothness. Comparisons with respect to some competitors are presented.