Generalized additive models for location, scale and shape

Generalized additive models for location, scale and shape

2005 | R. A. Rigby and D. M. Stasinopoulos
The paper introduces the Generalized Additive Model for Location, Scale and Shape (GAMLSS), a flexible statistical model for univariate response variables. Unlike traditional models such as generalized linear models (GLMs) and generalized additive models (GAMs), GAMLSS allows the modeling of not only the mean (location) but also the scale and shape parameters of the distribution of the response variable. This flexibility is achieved by using parametric and/or additive nonparametric functions of explanatory variables and random effects. The model can accommodate highly skewed or kurtotic continuous and discrete distributions, making it suitable for a wide range of applications. The GAMLSS framework incorporates both systematic and random parts of the model, with the systematic part allowing for the modeling of location, scale, and shape parameters as functions of explanatory variables and random effects. Maximum (penalized) likelihood estimation is used for model fitting, with algorithms such as Newton-Raphson or Fisher scoring for maximizing the likelihood. Additive terms are fitted using a backfitting algorithm, and censored data can be easily incorporated. The paper discusses various distributions that can be used within the GAMLSS framework, including the Beta-binomial, Box-Cox, and Student t distributions. It also covers specific types of additive terms such as cubic smoothing splines, random-walk terms, and spatial random-effect terms. The model is applied to five different data sets from various fields to demonstrate its generality and flexibility. The GAMLSS model is more general than GLMs, GAMs, GLMMs, and GAMMs, as it does not restrict the distribution of the response variable to the exponential family and allows all parameters of the distribution to be modeled as functions of explanatory variables and random effects. The paper also discusses model selection, inference, and residual diagnostics, emphasizing the importance of considering model uncertainty and using criteria such as the generalized Akaike information criterion (GAIC) for model selection. The algorithms used for fitting the GAMLSS model include the CG and RS algorithms, which are based on the Newton-Raphson or Fisher scoring method. These algorithms are implemented in the R package GAMLSS, allowing for the fitting of complex models with various types of additive terms and distributions. The paper concludes that the GAMLSS framework provides a powerful and flexible approach to modeling univariate response variables, with applications in a wide range of fields.The paper introduces the Generalized Additive Model for Location, Scale and Shape (GAMLSS), a flexible statistical model for univariate response variables. Unlike traditional models such as generalized linear models (GLMs) and generalized additive models (GAMs), GAMLSS allows the modeling of not only the mean (location) but also the scale and shape parameters of the distribution of the response variable. This flexibility is achieved by using parametric and/or additive nonparametric functions of explanatory variables and random effects. The model can accommodate highly skewed or kurtotic continuous and discrete distributions, making it suitable for a wide range of applications. The GAMLSS framework incorporates both systematic and random parts of the model, with the systematic part allowing for the modeling of location, scale, and shape parameters as functions of explanatory variables and random effects. Maximum (penalized) likelihood estimation is used for model fitting, with algorithms such as Newton-Raphson or Fisher scoring for maximizing the likelihood. Additive terms are fitted using a backfitting algorithm, and censored data can be easily incorporated. The paper discusses various distributions that can be used within the GAMLSS framework, including the Beta-binomial, Box-Cox, and Student t distributions. It also covers specific types of additive terms such as cubic smoothing splines, random-walk terms, and spatial random-effect terms. The model is applied to five different data sets from various fields to demonstrate its generality and flexibility. The GAMLSS model is more general than GLMs, GAMs, GLMMs, and GAMMs, as it does not restrict the distribution of the response variable to the exponential family and allows all parameters of the distribution to be modeled as functions of explanatory variables and random effects. The paper also discusses model selection, inference, and residual diagnostics, emphasizing the importance of considering model uncertainty and using criteria such as the generalized Akaike information criterion (GAIC) for model selection. The algorithms used for fitting the GAMLSS model include the CG and RS algorithms, which are based on the Newton-Raphson or Fisher scoring method. These algorithms are implemented in the R package GAMLSS, allowing for the fitting of complex models with various types of additive terms and distributions. The paper concludes that the GAMLSS framework provides a powerful and flexible approach to modeling univariate response variables, with applications in a wide range of fields.
Reach us at info@study.space