Appendix 3—table 2. Cross-sectional regression model classes based on functional vs. scalar predictor variables (i.e. covariates) and functional vs. scalar outcome variables.

We take the FoFR, FoSR, and SoFR to be the single-level (non-longitudinal) versions of these methods.

	Functional outcome	Scalar outcome
Functional predictors	Function-on-function regression (FoFR)	Scalar-onfunction regression (SoFR)
Scalar predictors	Function-onscalar regression (FoSR)	Generalized linear models (GLM)