Here are some useful online references that related to topics discussed during the workshop.
Modeling
tidyverse
Correlation and Regression
Multiple regression
http://ww2.coastal.edu/kingw/statistics/R-tutorials/multregr.html
http://www.r-bloggers.com/r-tutorial-series-multiple-linear-regression/
Nonlinear regression
Books and other articles
Nonlinear Regression with R: https://www.springer.com/la/book/9780387096155
Extending the Linear Model with R: https://www.crcpress.com/Extending-the-Linear-Model-with-R-Generalized-Linear-Mixed-Effects-and/Faraway/p/book/9781498720960