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what is Forocst function means
Posted: Tue Dec 05, 2006 7:41 am
by sally
hi,,
i want to use a function to do the forecasting----moving average. can i use Forcst function to do this?
Posted: Tue Dec 05, 2006 11:31 am
by bob@vensim.com
It is worth reading Sterman's book on this - the standard representation of expectations as formed by people is a SMOOTH function which is an exponentially weighted moving average.
Posted: Tue Dec 05, 2006 1:42 pm
by sally
if i only want to use simple moving agreage ?
which fuction should i use?
thank you .
Posted: Tue Dec 05, 2006 9:26 pm
by bob@vensim.com
To get a simple moving aveage use
moving average = period accumulation/averaging time
period accumulation = INTEG(value to average - outflow,init average value*averaging time)
outflow = DELAY FIXED(value to average,averaging time,init average value/averaging time)
still didn't know how to set up the forecast function
Posted: Thu Dec 07, 2006 2:22 pm
by sally
i am still confused about the forecasting function in vensim, i want to use the customer to forecasting the inventory level.
i want to use simple moving average ,,
hope some one can help me to figure it out..
thank you
Posted: Tue Feb 06, 2007 11:52 am
by sally
i still didn't know how to set up the forecast?
hope some one can help me
Posted: Tue Feb 06, 2007 1:44 pm
by bob@vensim.com
use
expected demand = SMOOTH(demand,time to form expectations) ~ Widget/Month
Time to form expectations = 5 ~ Month
Expected Inventory = MAX(0,Inventory + (expected production - expected demand) * Inventory Forecast Horizon) ~ Widget
Inventory Forecast Horizon = 4 ~ Month