Fig. 5: Scoring for a range of GAM spline parameters used to select the best performing combination.

a The median absolute error (b) bias, (c) prediction interval coverage and (d) interval score metrics for combinations of different numbers of basis functions in the hierarchical GAM. Models were evaluated on held out forecasting performance for 2-week projections, each week from 10 Nov 2022 to 08 Jan 2023.