State_time and calculation methods

[dtordrup]

This is probably not a bug, but a result of which model calculation method is used.

While model_time is always an integer, state_time assumes half-cycle values when the method = "life-table" parameter is used with run_model (state_time = 1.5, 2.5, 3.5 etc). In contrast, state_time assumes integer values when method = "begin" (2, 3, 4...) or method = "end" (1, 2, 3...) parameters are used.

This was slightly counter-intuitive given an integer evaluation used in the original paper by Filipovi´c-Pierucci and Zarca, i.e. (p. 6):

R> par_mod <- modify(
R+ par_mod,
R+
R+ cost_surg = 20000,
R+ cost_surg_cycle = ifelse(state_time == 1, cost_surg, 0))

It would help immensely to add the parameter options of method = ... to the run_model section of the heemod reference manual, along with their impact on the state_time variable.

Thanks for an excellent package!