Vensim PLE - forecasting

[Iss]

Hi,
Does anyone know if there is a function named FORECAST in Vensim PLE ?If there isn't, then is there another way to forecast in vensim ple, or some other function that would do it instead of forecast? I would be glad if someone shared that information with me:)

[LAUJJL]

Hi

Forecast is the equivalent of
FORECAST=input*(1+TRD*horizon)
TRD = ZIDZ(input-AV,average time*AV)
AV=INTEG((input-AV)/average time,ininput)
as explained when you consult the index of forecast in the help.
All this works in PLE, and if the zidz does not work it is transformable too in a simple equation, with an if then else.
You can use, smooth or trend too, that have their equivalent explained too in simple equations.
It is to my opinion better to use the detailed equations than the original equation, because it is easier to understand how the formula works. It is more visible and easier to modify if you want to change how the function works.
Regards.
JJ

[Iss]

Thank You for your help
Still, I can't find an equation that stands for AV, INTEG or TRD. The only equation that I see is ZIDZ, yet in order to count it I need to know value AV. And in order to count AV I need to know the INTEG, which to be counted needs AV:/ In that case, what is this AV and how to count it?:(

[bob@vensim.com]

The molecules have an example of a forecast formulation. You can download them from

http://www.vensim.com/freedownload.html

(select Moleucle) - install and read the documentation. The above equations are actually pretty self explanatory (and complete)- INTEG is the Integration function and ZIDZ is a Zero if Divide by Zero function.

[LAUJJL]

Hi

Here is the forecast equations in a model.
Regards.
JJ

[LAUJJL]

Hi

joined the right model, the previous was empty.
Regards.

[Iss]

Finally!
My model works:) Thank you for your indispensable help!I wouldn't manage to create that model without forecast. And now it works:)
Regards