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This open access book offers an introduction to mixed
generalized linear models with applications to the biological
sciences, basically approached from an applications perspective,
without neglecting the rigor of the theory. For this reason, the
theory that supports each of the studied methods is addressed and
later - through examples - its application is illustrated. In
addition, some of the assumptions and shortcomings of linear
statistical models in general are also discussed. An alternative to
analyse non-normal distributed response variables is the use of
generalized linear models (GLM) to describe the response data with
an exponential family distribution that perfectly fits the real
response. Extending this idea to models with random effects allows
the use of Generalized Linear Mixed Models (GLMMs). The use of
these complex models was not computationally feasible until the
recent past, when computational advances and improvements to
statistical analysis programs allowed users to easily, quickly, and
accurately apply GLMM to data sets. GLMMs have attracted
considerable attention in recent years. The word "Generalized"
refers to non-normal distributions for the response variable and
the word "Mixed" refers to random effects, in addition to the fixed
effects typical of analysis of variance (or regression). With the
development of modern statistical packages such as Statistical
Analysis System (SAS), R, ASReml, among others, a wide variety of
statistical analyzes are available to a wider audience. However, to
be able to handle and master more sophisticated models requires
proper training and great responsibility on the part of the
practitioner to understand how these advanced tools work. GMLM is
an analysis methodology used in agriculture and biology that can
accommodate complex correlation structures and types of response
variables.Â
This open access book focuses on the linear selection index (LSI)
theory and its statistical properties. It addresses the
single-stage LSI theory by assuming that economic weights are fixed
and known - or fixed, but unknown - to predict the net genetic
merit in the phenotypic, marker and genomic context. Further, it
shows how to combine the LSI theory with the independent culling
method to develop the multistage selection index theory. The final
two chapters present simulation results and SAS and R codes,
respectively, to estimate the parameters and make selections using
some of the LSIs described. It is essential reading for plant
quantitative geneticists, but is also a valuable resource for
animal breeders.
This book is open access under a CC BY 4.0 license This open access
book brings together the latest genome base prediction models
currently being used by statisticians, breeders and data
scientists. It provides an accessible way to understand the theory
behind each statistical learning tool, the required pre-processing,
the basics of model building, how to train statistical learning
methods, the basic R scripts needed to implement each statistical
learning tool, and the output of each tool. To do so, for each tool
the book provides background theory, some elements of the R
statistical software for its implementation, the conceptual
underpinnings, and at least two illustrative examples with data
from real-world genomic selection experiments. Lastly, worked-out
examples help readers check their own comprehension.The book will
greatly appeal to readers in plant (and animal) breeding,
geneticists and statisticians, as it provides in a very accessible
way the necessary theory, the appropriate R code, and illustrative
examples for a complete understanding of each statistical learning
tool. In addition, it weighs the advantages and disadvantages of
each tool.
This open access book focuses on the linear selection index (LSI)
theory and its statistical properties. It addresses the
single-stage LSI theory by assuming that economic weights are fixed
and known - or fixed, but unknown - to predict the net genetic
merit in the phenotypic, marker and genomic context. Further, it
shows how to combine the LSI theory with the independent culling
method to develop the multistage selection index theory. The final
two chapters present simulation results and SAS and R codes,
respectively, to estimate the parameters and make selections using
some of the LSIs described. It is essential reading for plant
quantitative geneticists, but is also a valuable resource for
animal breeders.
Current trends in population growth suggest that global food
production is unlikely to satisfy future demand under predicted
climate change scenarios unless rates of crop improvement are
accelerated. In order to maintain food security in the face of
these challenges, a holistic approach that includes stress-tolerant
germplasm, sustainable crop and natural resource management, and
sound policy interventions will be needed. The first volume in the
CABI Climate Change Series, this book provides an overview of the
essential disciplines required for sustainable crop production in
unpredictable environments. Chapters include discussions of
adapting to biotic and abiotic stresses, sustainable and
resource-conserving technologies and new tools for enhancing crop
adaptation. Examples of successful applications as well as future
prospects of how each discipline can be expected to evolve over the
next 30 years are also presented. Laying out the basic concepts
needed to adapt to and mitigate changes in crop environments, this
is an essential resource for researchers and students in crop and
environmental science as well as policy makers.
This book is open access under a CC BY 4.0 license This open access
book brings together the latest genome base prediction models
currently being used by statisticians, breeders and data
scientists. It provides an accessible way to understand the theory
behind each statistical learning tool, the required pre-processing,
the basics of model building, how to train statistical learning
methods, the basic R scripts needed to implement each statistical
learning tool, and the output of each tool. To do so, for each tool
the book provides background theory, some elements of the R
statistical software for its implementation, the conceptual
underpinnings, and at least two illustrative examples with data
from real-world genomic selection experiments. Lastly, worked-out
examples help readers check their own comprehension.The book will
greatly appeal to readers in plant (and animal) breeding,
geneticists and statisticians, as it provides in a very accessible
way the necessary theory, the appropriate R code, and illustrative
examples for a complete understanding of each statistical learning
tool. In addition, it weighs the advantages and disadvantages of
each tool.
This open access book offers an introduction to mixed
generalized linear models with applications to the biological
sciences, basically approached from an applications perspective,
without neglecting the rigor of the theory. For this reason, the
theory that supports each of the studied methods is addressed and
later - through examples - its application is illustrated. In
addition, some of the assumptions and shortcomings of linear
statistical models in general are also discussed. An alternative to
analyse non-normal distributed response variables is the use of
generalized linear models (GLM) to describe the response data with
an exponential family distribution that perfectly fits the real
response. Extending this idea to models with random effects allows
the use of Generalized Linear Mixed Models (GLMMs). The use of
these complex models was not computationally feasible until the
recent past, when computational advances and improvements to
statistical analysis programs allowed users to easily, quickly, and
accurately apply GLMM to data sets. GLMMs have attracted
considerable attention in recent years. The word "Generalized"
refers to non-normal distributions for the response variable and
the word "Mixed" refers to random effects, in addition to the fixed
effects typical of analysis of variance (or regression). With the
development of modern statistical packages such as Statistical
Analysis System (SAS), R, ASReml, among others, a wide variety of
statistical analyzes are available to a wider audience. However, to
be able to handle and master more sophisticated models requires
proper training and great responsibility on the part of the
practitioner to understand how these advanced tools work. GMLM is
an analysis methodology used in agriculture and biology that can
accommodate complex correlation structures and types of response
variables.Â
Current trends in population growth suggest that global food
production is unlikely to satisfy future demand under predicted
climate change scenarios unless rates of crop improvement are
accelerated. In order to maintain food security in the face of
these challenges, a holistic approach that includes stress-tolerant
germplasm, sustainable crop and natural resource management, and
sound policy interventions will be needed. The first volume in the
CABI Climate Change Series, this book provides an overview of the
essential disciplines required for sustainable crop production in
unpredictable environments. Chapters include discussions of
adapting to biotic and abiotic stresses, sustainable and
resource-conserving technologies and new tools for enhancing crop
adaptation. Examples of successful applications as well as future
prospects of how each discipline can be expected to evolve over the
next 30 years are also presented. Laying out the basic concepts
needed to adapt to and mitigate changes in crop environments, this
is an essential resource for researchers and students in crop and
environmental science as well as policy makers.
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