Error Message

[reza1999]

hi everyone
I have encountered some errors in simulating Vensim.the error says variable 'not used in the model'
I chose the 'supplementary' option but it was not cleared.
and another error is 'simultaneous equation involving : (variable)'

thanks.

[Administrator]

It's impossible to help you unless you upload the model.

Setting a variable as 'supplementary' should clear the warning. It's not an error, it's telling you that you have a calculation that is not used.

Simultaneous equations means you've probably got an error in the logic of your model.

[reza1999]

Hello again.
This is my model that errors on

[Administrator]

The equation for "qpd0" is clearly incorrect. You cannot use "qpd0" to calculate "qpd0".

qpd0 = IF THEN ELSE(TPD=0, IF THEN ELSE(HD-qpd0>=qp-qpd0, qp-qpd0 , qp-qpd0*HD-qpd0/qp-qpd0 ) , 0 )

It's difficult to offer any advice here. I have no idea what "qpd" means and as there are no units in the model, it's impossible to guess.

[reza1999]

Actually I used the equation from this article for my college project.
That's weird for me too. I have no idea about it.
I asked my teacher and he said that might be a 'recursive function'.
Any ideas?
Thank you.

[Administrator]

All I can suggest is start at section 4.3 of that document and implement each equation 1 at a time.

It's not something I would want to do. It looks awful.

PS. I've removed the paper as you need the author's permission to post on a public forum such as this.

[tomfid]

The subscript on QPD0 on the left side is vcd, and on the right side it's vc'd or vcd'. I'm not sure if the ' (prime) refers to differentiation or something else, but it's possible that the left and right side expressions are distinct things.