Empty LISTVAR

almoon · Post by **almoon** » Sun Nov 07, 2010 8:39 pm

I have a problem with the listvar it keeps give me that the listvar is empty so what is going on ?

do I need to change anything in my model to make it work ?

Post by **Administrator** » Sun Nov 07, 2010 11:55 pm

Can you post anything here that demonstrates the error?

bob@vensim.com · Post by **bob@vensim.com** » Mon Nov 08, 2010 11:42 am

The message occurs when the variable referred to is not a constant (or a gaming variable in game mode)

almoon · Post by **almoon** » Mon Nov 08, 2010 2:27 pm

LISTVAR,"FINAL TIME",88,24,7,4,L|System|10|B|255-0-0,[0|60]10|20|30|40|50|60

so this is what I wrote, so what do you think the problem?

Post by **Administrator** » Mon Nov 08, 2010 3:12 pm

Are you running a game while trying to access the listbox?

almoon · Post by **almoon** » Mon Nov 08, 2010 3:15 pm

Post by **Administrator** » Mon Nov 08, 2010 5:50 pm

That's the reason. FINAL TIME is a constant, you cannot modify it during a game (you can only change it before the game starts).

almoon · Post by **almoon** » Mon Nov 08, 2010 6:58 pm

mmmm and am not sure how to do that...

Post by **Administrator** » Mon Nov 08, 2010 7:48 pm

Have a screen where you set constants (like final time etc). Then move to a new screen when you start the run where you can change the gaming decisions.

almoon · Post by **almoon** » Tue Nov 09, 2010 11:55 am

Thanks, I did that but the problem is still available ,,,

but I was thinking is the final time is the same one in the model when we put the setting of the model?

maybe from there the problem ?

bob@vensim.com · Post by **bob@vensim.com** » Wed Nov 10, 2010 10:45 am

You need to look at the equation for FINAL TIME. Normally this is a constant, but many models, especially project models, make this a variable. If it is not a constant you won't be able to change it. I would not recommend making FINAL TIME a game variable.

A more useful question might be why you would want to change FINAL TIME anyway? If the user is tired of the game they can just stop playing.