IPS-003 (2023)

Data Analysis and Design of Experiments

‘ggplot2’ Basics
The Layered Grammar of Graphics
Pedro J. Aphalo
2023-05-03
abstract Currently, ‘ggplot2’ and its extensions are the most popular approach to data visualization in R. Plot construction with these R packages is based on a Layered Grammar of Graphics for building data visualizations. In this page I explain how ‘ggplot2’ plots are assembled and later rendered. The main focus is on the grammar used and how its features determine how we build plots.
EDA with ‘ggplot2’
EDA = Exploratory Data Analysis
Pedro J. Aphalo
2023-05-24
abstract EDA and ‘ggplot2’ have a common ancestry. EDA as originally proposed by John W. Tukey included data visualization as a key tool. In this page I show examples of some of the data visualizations that are used in EDA, together with the R code I used to create them. I also briefly describe EDA’s position in the scientific research process and mention its origins.
Model fitting in R
An introduction using lm()
Pedro J. Aphalo
2023-05-30
abstract In this page I give a brief presentation on the mechanics of fitting statistical models to observed data using R. I use a lineal model (LM), polynomial regression, as example. I describe the most important values contained in the model fit object returned by function lm() and how to extract them. I rely heavily on diagrams and data plots.
P-values, R2, AIC, BIC
How do they fit into the research process?
Pedro J. Aphalo
2023-08-19
abstract Fortuitously, in the last few days I have several times have had to ponder about the roles of hypothesis-based and descriptive approaches to research. Being an agronomist and ecologist rather than a philosopher, the question that worries me is how data analysis differs between these two approaches and how we should interpret the results of the analysis in each case. This page collects some of my thoughts and opinions on the subject at the time of writing.
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