how to have a stock variable that zeros at a specific time step?

[Noorgm]

I have a model that is supposed to calculate Transit ridership, and I have unit of time set to Year but time step set to daily (1/365) , most of the calculations done are daily except birth and death rates.

Daily Transit ridership is calculated and I want to have a way to see the total rides in a year, so add up all rides from each day.

I considered a stock variable but I don't know of a way to make it go back to zero at the beginning of each year in the simulation. Should i be using a stock variable or a stock variable? and how can I zero the total rides each year? or should i change the models time unit?

The model is attached below.

[Administrator]

The time step in the model is one year, not 1/365. There is guidance in the Vensim help system on how to select an appropriate time step. In this model, I would probably use day as a time measurement, not year.

To reset a level you can do something like this.

level = integ (inflow-outflow,initial value)

outflow = level / time step


I'd strongly urge you to add units to the model and make sure it passes this test.

[Noorgm]

Thank you for the replay, it was really helpful.

Regarding the Outflow I want to check if I understand what you mean

If the models measurement is in days and the time step is also a day and Yearly transit ridership is a level with formula (daily transit ridership- outflow, initial value)

The outflow would be = Yearly transit ridership/Day -> Level/Time Step?

I am unsure of how that would collect the yearly ridership in this case and subtracts it.

Am I missing something or is your suggestion based on different time settings?

[Noorgm]

Also how would the population be calculated given that the birth rate is in years