Simultaneous equations impossible to solve

[luisangelguzmang]

Hi, i'm building a model, but the simultaneous equations problem is unsolvable to me. I was trying to the simultaneous and fin zero functions, but did not work. The problem is (I think), that I use one variable (IVT car ij) to calculate a loop with many others, so I don't know where is the starting (or ending). Can you help me??
I would be very grateful.
The model is attached

[Administrator]

I cannot check the model at the moment, it's complaining about "Sheet #Trb TM opeak not found in data.xlsx.

[luisangelguzmang]

Sorry! here it goes again...

[Administrator]

There is nothing I can suggest here. Things like "ivt car ij" mean nothing to me (no units or description either to give a clue to what it is).

Check your formulation. There has to be a delay somewhere in the system, or a level.

[tomfid]

I can't really tell what's going on without informative variable names, but your "tcur increases" which is (tcur ij[i,J,ToD]/"tcur ij t-1"[i,J,ToD]) is strongly suggestive of a stock adjustment process.

I think if you reformulate that as tcur = INTEG( change in tcur, initial tcur ) with change in tcur = f(whatever), you might be OK.

[naserprs87]

Hi Guys,
I have a loop in my model, and I can't figure out how I should remove the "simultaneous initial value" error.
In order to break the loop, I used "active initial" for one of the rates in the model, and it solved the error, but now, this initial value is influencing all the other stocks and rates in the model. For instance, in time 0, all the other rates starts removing some amount from the stocks and make them negative. I can use a switch for those rates that shouldn't work at time 0, but then all the rates and stocks get to zero.
Do you have any suggestion?

[Administrator]

You'll need to upload your model so we can take a look.

[naserprs87]

Here you are.
I used "active initial" for the input of eggs.

[Administrator]

I'd suggest that "adults laying eggs" should be a level, it's a count of the number of adults laying eggs.

"Eggs" is probably not right either. I'd call it "unhatched eggs", the rate this increases is "adults * number of eggs per adult", it decreases based on how long they take to hatch (birth rate).

Hope this helps you get moving again.

[naserprs87]

Thank you so much