New modeler asking for help

[agnesnomore]

Dear all,

I am new to modeling and system dynamics, thus I seek help from you.
I built a model, it is based on Bass diffusion model of adoption. The story behind is: at the university I am doing my doctorate, there is a consumer food cooperative ran by volunteers (students and university academics/ non academics). I am trying to look at the student adoption to buy from there (the food is healthy, nutritious, chemical-free and ethically produced but the sales are not the same after covid). But model stops after running, giving floating point error for "ratio of students buying from market" variable. Could you please help me fix my model?

Thanks.

Pinar

[Administrator]

I've got the model running for you, but there is still some debugging to do.

"Students buying from BÜKOOP" goes negative as you are removing more from the stock than is available. So I've changed the equation to
min ( Students buying from BÜKOOP / TIME STEP , Students buying from BÜKOOP * disadoption rate )

"Students buying from market" goes negative as you are removing more from the stock than is available. So I've changed the equation to
min ( Students buying from market / TIME STEP
, reference adoption rate
* effect of ratio of students buying from market on adoption rate
* effect of comparative prices on adoption
* effect of comparative quality on adoption
* effect of comparative operating hours on adoption
* product satisfaction )

This causes a division by zero in "BÜKOOP product demand", so change equation to
zidz ( Students buying from BÜKOOP , monthly product demand per student )

"product availability" causes division by zero, so change to
zidz ( Products in BÜKOOP , BÜKOOP product demand )

[agnesnomore]

Thank you very much for your help and time. Wish you a great day.