Negative Stock

[nadia]

Hye everybody,

Why stock become negative? When I try extreme condition test my stock become negative.But, the others variables behave appropriately. Only the stock become negative.Anybody please help me. Is that possible if I attach my model and get comment for improvement in my model. Really need your help. Thank you in advance.


Regards,
Nadia.

[Administrator]

See the following thread. It should help.

http://www.ventanasystems.co.uk/forum/v ... ock#p14605

Or post your model here so we can take a look.

Tony.

[nadia]

Hi,

My model as attached. Hope I can get comments and suggestions for improvement for my model. Thank you.


Nadia.

[Administrator]

Try the following modifications.

local supply = min ( Rice Stock / time step , FRACTION STOCK RELEASE * Rice Stock )

What this equation does is take "what you want" (FRACTION STOCK RELEASE * Rice Stock) out of the stock, but if there is not enough, it completely empties the stock (Rice Stock / time step)

rice stock release = min ( gap in import , Rice Stock / time step - local supply )

This equation is similar to the local supply equation, you take out what you want (gap in import) or what is available (Rice Stock / time step minus anything taken out by "local supply").

This will stop the stock going negative.

Hope this helps.

Tony.

[nadia]

Ok.Thank you very much. It really helps me a lot.But what about the farmers net income? Where I can get the info about how to use min function?Thank you in advance.


Nadia.

[Administrator]

Where I can get the info about how to use min function?

It's just MINIMUM. STOCK / TIME STEP is the rate the empty the entire stock in one time step. So you take out the minimum of everything (stock/time step) or what you actually want to take out.

You can think of it as
IF THEN ELSE ( what you want to take out > STOCK , what you want to take out , STOCK / TIME STEP )

I hope this makes sense.