Fig. 1

Geometric mean plasma C-peptide (pmol/l) by age at onset and duration. A smoothed fit of log C-peptide to age at onset and duration was computed by LOESS regression of polynomial degree 2 and span 0.25, then evaluated over a grid of values of the predictor variables. The C-peptide level (pmol/l) of each panel is encoded both as its colour and as its coordinate on the vertical axis