Elastic net model formulations.

We use figurative equations to represent the different models, using i to index the current antibiotic in question. Covariates wi indicate host animal, xi indicate presence/absence of genes in the relevant set (x for all AMR genes, not just those in the relevant set), vi indicate presence/absence of any relevant gene, and zi the count of observed relevant genes. Operator * indicates interactions considered, while + indicates main effects only. See text for a detailed explanation of each model.