HP 12c Platinum Reference Manual page 90

90 Forecasting
Forecasting:
RPN Mode:
1. Key in the number 1 and press \ .
2. Key in the selected α and press ? 0 -? 1.
ALG Mode:
1. Key in the number 1 and press - .
2. Key in the selected α and press ? 0 ³? 1.
3. From the selection routine or from a previous forecast:
Key in the smoothed average S
Key in the trend T
Key in the forecast D ˆ
4. Key in the current data value and press t . The output is the error in forecasting the
value just entered.
5. Press t . The displayed value represents the forecast for the next period.
6. Record the following values: : 0 (α), : 2 (S
use as initial values in the next forecast. You may also wish to record : 5 (D
7. Repeat steps 4, 5, and 6 for the next forecast if available.
Example: Select the best smoothing constant based on sales (in thousands of dollars) of
22, 23, 23, 25, 23, 27, 25. Given the current sales in month 8 of 26, forecast the following
month.
Select the smoothing constant (α ):
12c platinum / 12C
RPN Keystrokes
fCLEARH
1\
.5?0-
?1
22?2
23?6t
t
23tt
25tt
23tt
27tt
25tt
:4
:0
and press ? 2.
t-1
and press ? 3.
t-1
and press ? 6.
t+1
12c platinum
ALG Keystrokes
fCLEARH
1-
.5?0³
?1
22?2
23?6t
t
23tt
25tt
23tt
27tt
25tt
:4
:0
), : 3 (T
t-1
Display
0.00
1.00
0.50
0.50
22.00
0.00
23.00
23.25
25.25
23.69
27.13
25.95
Cumulative error ( ∑ e
23.61
Smoothing constant (α ).
0.50
) and : 6 D ˆ
(
t-1 t+1
).
t
Comments
2
).
) for