A causal inference perspective on the analysis of compositional data

Compositional data comprise the parts of some whole, for which all parts sum to that whole. They are prevalent in many epidemiological contexts. Although many of the challenges associated with analysing compositional data have been discussed previously, we do so within a formal causal framework by utilizing directed acyclic graphs (DAGs).We depict compositional data using DAGs and identify two distinct effect estimands in the generic case: (i)...