Hi, I'm new to vensim, it may be a basic question
I do have two variables ("media pressure" and "time of remembrance") which are inputs for "desire to donate".
"Desire to donate" should be a sum of "media pressure" (dmnl) for the "time of remembrance" (days).
E.g., if time of remambrance is 4 => desire to donate(T) = media pressure(T-1) + media pressure(T-2) + media pressure(T-3) +media pressure(T-4)
Is that possible? And putting all that in an information delay function?
Grateful for any/every help
Variable depending on time +delay
Re: Variable depending on time +delay
I know exactly what you mean - this sounds like a variation on what marketing science types call an adstock transformation.
You can use a discrete delay, but I'd encourage you to make this a continuous process, because it's more realistic for people to gradually forget media exposure, than to have its effect end abruptly after some time.
Here's one way to do it:
- create a stock of "desire to donate"
- inflow: "creating desire" depends on media exposure
- outflow: "forgetting" = desire/time to forget
This is linear - if you want it nonlinear, to capture saturation, you might instead do:
- stock of cumulative media exposure
- inflow: exposure to messages
- ouflow: forgetting (as above)
Then desire = f(cumulative exposure), with f() as an expression, or a lookup for convenience.
Wish I could say more, but I have to catch a plane. Good luck.
You can use a discrete delay, but I'd encourage you to make this a continuous process, because it's more realistic for people to gradually forget media exposure, than to have its effect end abruptly after some time.
Here's one way to do it:
- create a stock of "desire to donate"
- inflow: "creating desire" depends on media exposure
- outflow: "forgetting" = desire/time to forget
This is linear - if you want it nonlinear, to capture saturation, you might instead do:
- stock of cumulative media exposure
- inflow: exposure to messages
- ouflow: forgetting (as above)
Then desire = f(cumulative exposure), with f() as an expression, or a lookup for convenience.
Wish I could say more, but I have to catch a plane. Good luck.
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Blog: http://blog.metasd.com
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Re: Variable depending on time +delay
Thank you, tomfid
It worked perfectly!
It worked perfectly!