Seasonal Variation Factors Based On Centered Moving Averages - HP 12c Platinum Reference Manual

78 Forecasting
12c platinum / 12C
RPN Keystrokes
300500t
271120t
Seasonal Variation Factors Based on
Centered Moving Averages
Seasonal variation factors are useful concepts in many types of forecasting. There are
several methods of developing seasonal moving averages, on the of more common ways
being to calculate them as a ratio of the periodic value to a centered moving average for
the same period.
For instance, to determine the sales for the 3rd quarter of a given year a centered moving
average for that quarter would be calculated from sales figures from the 1st, 2nd, 3rd and
4th quarters of the year and the 1st quarter of the following year. The seasonal variation
factor for that 3rd quarter would then be the ratio of the actual sales in the 3rd quarter to
the centered moving average for that quarter.
While quarterly seasonal variations are commonly used, the HP 12C Platinum can also be
programmed to calculate monthly seasonal variations using a centered 12 month moving
average. Programs for both of these calculations are represented here:
An HP 12C Platinum program to calculate the quarterly seasonal variations based on a
centered 4-point moving average is:
12c platinum / 12C
RPN KEYSTROKES
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2
z
:2
?1
+
:3
?2
+
:4
?3
+
:5
?4
2
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12c platinum
ALG Keystrokes
300500t
271120t
DISPLAY
000,
1 :1
001, 45
2 z
002,
10 2
003,
2 +
004, 45
1 :2
005, 44
40 ?1
006,
3 +
007, 45
2 :3
008, 44
40 ?2
009,
4 +
010, 45
3 :4
011, 44
40 ?3
012,
5 ³
013, 45
4 :5
014, 44
2 ?4
015,
10 z
016,
40 2
017,
Display
207,440.00 3-month average for May.
234,460.00 3-month average for June.
12c platinum
ALG KEYSTROKES
fs
fCLEARÎ
Comments
DISPLAY
000,
001, 45 1
002, 10
003, 2
004, 40
005, 45 2
006, 44 1
007, 40
008, 45 3
009, 44 2
010, 40
011, 45 4
012, 44 3
013, 36
014, 45 5
015, 44 4
016, 10
017, 2