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the results are different as they should 1 month 15 hours ago #507

Hello,
i have built my model. when STAN calculated everything, i found something strange about it. i have defined that the stock change of a process (Wasserkörper in attached model) in all of the periods must end up in a flow (ins Meer). But that was not completely taken into action. The stock changes over time although that does not have to be the case as i defined a relation for that.
i attach my model as well for better understanding what i mean.
Do i have to change something? what should i do to make this work?
Thanks
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the results are different as they should 1 month 14 hours ago #508

i gave the stock value 0 in each period and it works!

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the results are different as they should 1 month 13 hours ago #509

Sorry, but I think there might be something wrong with your understanding of the function of a stock:
(1) The change in stock in a certain period is the difference of what is going into a process in this period minus what is going out of it.
(2) The stock at the start of a period (this is actually what is displayed in the stock symbol) is the stock at the start of the previous period + the change in stock in this previous period.
So, the stock and the change in stock are interconnected and cannot be set independently. But maybe I have misunderstood your intentions.
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the results are different as they should 4 weeks 1 day ago #510

this problem is now fixed. Thank you I understood it.
but I still have a question and that is I have modeled a storage function. in my model which can also be seen above that within two processes a few flows come in and in the 4th month everything must flow out. but the problem is that in the 4th month I also have a few flows that I would like to flow out with the stock. I have added the flows in the 4th month with the values of the 3rd month, so that everything could flow out in 4th month.
but it is not possible to tell STAN that value of a flow in Period = stock in the same period + stock change of the same period. Correct?
so what i have done is actually what i can do with my problem or is there any other way to model this situation?
best regards

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the results are different as they should 4 weeks 1 day ago #511

Yes, it it is possible to model the behaviour you described with STAN! The only thing that you have to do is to state with an additional relation that the change in stock(!) in month 4 is -1 times the material in stock at the beginning of month 4. And, of course, you have to set the outputs of the stock in the periods 1 to 3 and the starting stock in period 1 to be zero. See attached example.
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