Search results for "Linear regression"
showing 10 items of 375 documents
1H and13C NMR spectroscopy of brominated diphenyl ethers. A multiple linear regression analysis
2000
The 1H and 13C NMR chemical shifts and 1H, 1H coupling constants of 27 brominated diphenyl ethers are reported. The increment models for the bromine substituent effects on the 1H and 13C NMR chemical shifts were constructed based on a multiple linear regression analysis. In addition to the single substituent effects, two particle increments and corrective terms for conformational effects are included in these models in order to obtain a reliable prediction of chemical shifts. Copyright © 2000 John Wiley & Sons, Ltd.
A statistical study of the additivity of substituent effects on the5J(HH) long-range coupling constant of the formyl proton in substituted benzaldehy…
1982
The additivity of chloro and hydroxy substituent effects on the formyl proton spin-spin coupling constants with the meta ring proton, 5J(HH), has been tested with 15 chlorinated benzaldehydes and hydroxybenzaldehydes by multiple linear regression analysis. No general additivity rule was detected with whole data. Using benzaldehyde as the reference substance, a good correlation was achieved for p-hydroxybenzaldehydes. The same reference compound was not suitable for o-hydroxy derivatives; a much better correlation was observed using o-hydroxybenzaldehyde as a reference compound in the latter case.
Fast-multivariate optimization of chiral separations in capillary electrophoresis: Anticipative strategies
2014
Abstract The design of experiments (DOE) is a good option for rationally limiting the number of experiments required to achieve the enantioresolution (Rs) of a chiral compound in capillary electrophoresis. In some cases, the modeled Rs after DOE analysis can be unsatisfactory, maybe because the range of the explored factors (DOE domain) was not the adequate. In these cases, anticipative strategies can be an alternative to the repetition of the process (e.g. a new DOE), to save time and money. In this work, multiple linear regression (MLR)-steepest ascent and a new anticipative strategy based on a multiple response-partial least squares model (called PLS2-prediction) are examined as post-DOE…
Data Augmentation Approach in Bayesian Modelling of Presence-only Data
2011
Abstract Ecologists are interested in prediction of potential distribution of species in suitable areas, essential for planning conservation and management strategies. Unfortunately, often the only available information in such studies is the true presence of the species at few locations of the study area and the associated environmental covariates over the entire area, referred as presence-only data. We propose a Bayesian approach to estimate logistic linear regressions adapted to presence-only data through the introduction of a random approximation of the correction factor in the adjusted logistic model that allows us to overcome the need to know a priori the prevalence of the species.
What is the best fitting function? Evaluation of lactate curves with common methods from the literature
2015
Using the lactate threshold for training prescription is the gold-standard, although there are several open questions. One open question is: What is the best fitting method for the load-lactate data points? This investigation re-analyses over 3500 lactate diagnostic datasets in swimming. Our evaluation software examines six different fitting methods with two different minimization criteria (RMSE and SE). Optimization of parameters of the functions is put in excecution with gradient descent. From a mathematical point of view, the double phase model, which consists of two linear regression lines, shows the least errors (RMSE min 0.254 ± 0.172; SE min 0.311 ± 0.210). However, this method canno…
The Analysis of Auxological Data by Means of Nonlinear Multivariate Growth Curves
1999
In this paper we treat the problem to analyse a data set constituted by multivariate growth curves for different subjects; thus in this context we deal with 3-way data tables. Nevertheless, it is not possible using factorial techniques proposed to deal with 3-way data matrices, because the observations are generally not equally spaced; moreover a multilevel approach founded on polynomial models is not suitable to deal with intrinsic nonlinear models. We propose a non-factorial technique to analyse auxological data sets using an intrinsic nonlinear multivariate growth model with autocorrelated errors. The application to a real data set of growing children gave easily interpretable results.
Land surface air temperature retrieval from EOS-MODIS images
2014
The knowledge of the spatial and temporal patterns of surface air temperature (SAT) is essential to monitor a region's climate and meteorology, to quantify surface exchange processes, to improve climatic and meteorological model results, and to study health and economic impacts. This letter analyzed correlations between SAT and geophysical land surface variables, mainly land surface temperature (LST), to establish operative techniques to obtain spatially continuous land SAT maps from satellite data, unlike data provided by meteorological station networks. The correlations were analyzed by using EOS-MODIS images, meteorological station network data, and geographical variables. Linear regress…
Building energy performance forecasting: A multiple linear regression approach
2019
Abstract Different ways to evaluate the building energy balance can be found in literature, including comprehensive techniques, statistical and machine-learning methods and hybrid approaches. The identification of the most suitable approach is important to accelerate the preliminary energy assessment. In the first category, several numerical methods have been developed and implemented in specialised software using different mathematical languages. However, these tools require an expert user and a model calibration. The authors, in order to overcome these limitations, have developed an alternative, reliable linear regression model to determine building energy needs. Starting from a detailed …
Fourier transform infrared determination of Fluometuron in pesticide formulations
2003
Abstract A single method has been developed for Fourier transform infrared (FTIR) determination of Fluometuron in pesticide formulations. Samples were ultrasonically shaken with CHCl3 for 5 min and the FTIR spectra of sample extracts and standards were obtained at a nominal resolution of 4 cm−1 from 4000 to 900 cm−1 accumulating 25 scans. Fluometuron determination is based on the measure of peak area from 1342 to 1321 cm−1 corrected using a baseline defined from 1352 to 1294 cm−1. This procedure provided a limit of detection of 6.5 μg g−1, a sensitivity of 0.852 a.u. g mg−1 for a pathlength of 0.11 mm, a relative standard deviation of 1.6% for three analysis of a sample containing 50.4% (w/…
Identification of Leguminosae gums and evaluation of carob-guar mixtures by capillary zone electrophoresis of protein extracts.
2002
A procedure for the extraction and capillary zone electrophoresis (CZE) separation of proteins from carob, guar and tara gums in a background electrolyte (BGE) of pH 9 containing 0.1% polyvinyl alcohol is described. The CZE protein profiles exhibit characteristic peaks for each one of the Leguminosae gums, which can be used to construct models capable of identifying samples of carob, guar and tara gums, and predicting the guar content in binary carob-guar mixtures of different geographical origin and harvested in different years. The classification and prediction models are constructed by using linear discriminant analysis (LDA) and multiple linear regression (MLR), respectively. An excelle…