on 06-23-2009 5:54 PM
Hi Experts,
Could you please help me how below values are getting populating.
History Ex-Post
Jan 2,000
Feb 1,520 2,000
Mar 2,000 1,856
Apr 2,520 1,899
May 1,520 1,899
Jun 2,520 1,899
Jul 1,520 1,865
Aug 2,500 1,762
Sep 1,500 1,791
Oct 2,500 1,704
Nov 1,500 1,943
Dec 2,000 1,810
I am using Forecast model with parameters: Constant model 10
Alpha- 0.30 & Sigma- 1.25, Outlier- Expost
Could you please help me on the same.
Thanks
Hitesh
Hi Hitesh,
This question is marked as answered... are you still having issue?
Just in case it looks like you are trying to calculate the ex-post forecast.
Well since you are using a constant model, the formula is quite easy:
you have only a base forecast and only the alpha facvtor is used.
First ex post is for 2nd iteration: it is eaul to the first iteration of history.
In your case 2000
then you use the following formula
expost(n)=history(n-1) * alpha + ex-post(n-1)*(1-alpha)
let's say: E(n)=H(n-1)A+E(n-1)(1-A)
in your case:
E3=15200.3+20000.7=1856
E4=20000.3+18560.7=1899
This way
E5 should be equal to 2085.
That is were the automatic correct happen:
because aprile value 2500 is outside the boundaries the outlier correct it a give it the value of the ex post: 1899.
Then for sure the expost stay the same (E5=18990.3+18990.7=1899!)
Now how are the boundarie calculated?
If I remeber well based on the MAD: mean absole deviation.
in you case for april
MAD= (|1520-2000|+|2000-1856|)/2=312
MAD*sigma=390
And the deviation=2520-1899=621
So the deviation is bigger than the boundarie: the value is corrected by the outlier!
I hope it is readable!
Thanks and Regards
Julien
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I am still working on it.
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Hi Hitesh,
Just gone through following link. You will find the formuleas of diffrent forecast model. In that you will find the how does system calculate expost forecast & other things also.
Actualy this sheet made by Percx (SDN Member). Now same i am sharing with you.
Link is : APO Basic FC Models xl
Hope this will help You.
Regards
Sujay
Edited by: Sujay Joshi on Jun 24, 2009 10:50 AM
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Thanks Sujey,
I have gone through the sheet, and helped me.
Few doubts:
It is caluculating 3 Cycles, what is that and can we customize these cycles to 1.
And while going for next cycle, it is rolling value to period-1, but how it is calculating last period.
As if you check the 1st Ord. Exp Smoothing, and cycle 2, period = -1 Value= 38?
Thanks for your help!
Hitesh
History -
Ex-Post
Jan -
2,000
Feb----
1,520 -
2,000
Mar----
2,000 -
1,856
Apr----
2,520 -
1,899
May----
1,520 -
1,899
Jun----
2,520 -
1,899
Jul----
1,520 -
1,865
Aug -
2,500 -
1,762
Sep -
1,500 -
1,791
Oct -
2,500 -
1,704
Nov -
1,500 -
1,943
Dec -
2,000 -
1,810
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