SpaDES modules commonly use approximate durations that divide with no
remainder among themselves.
For example, models that simulate based on a "week" timestep, will likely
want to fall in lock step with a second module that is a "year" timestep.
Since, weeks, months, years don't really have this behaviour because of:
leap years, leap seconds, not quite 52 weeks in a year, months that are of
different duration, etc.
We have generated a set of units that work well together that are based on
the astronomical or "Julian" year.
In an astronomical year, leap years are added within each year with an extra
1/4 day, (i.e., 1 year == 365.25 days); months are defined as year/12, and
weeks as year/52.
dhour(x) dday(x) dyears(x) # S4 method for numeric dyears(x) dmonths(x) # S4 method for numeric dmonths(x) dweeks(x) # S4 method for numeric dweeks(x) dweek(x) dmonth(x) dyear(x) dsecond(x) dNA(x) # S4 method for ANY dNA(x)
numeric. Number of the desired units
Number of seconds within each unit
When these units are not correct, a module developer can create their own
time unit, and create a function to calculate the number of seconds
in that unit using the "d" prefix (for duration), following the
lubridate package standard:
ddecade <- function(x) lubridate::duration(dyear(10)).
Then the module developer can use "decade" as the module's time unit.