TrendBasedForecastTrend-based forecast for an exponentially growing quantity |
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Diagram
Information
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The trend-based forecast makes use of a perceived present condition and a fractional growth rate computed by a →Trend block that follows the model proposed by Sterman [3, pp. 34 - 38].
The perceived present condition (PPC) will be "brought forward" to the actual time using linear extrapolation:
Extrapolated Present Condition = Perceived Present Condition · ( 1 + fractional growth rate · time to perceive present condition)
The actual forecast is then arrived at by using exponential growth and continuous compounding:
forecast = extrapolated present condition · EXP( fractional growth rate · forecast horizon)
See also
Parameters (6)
| initialTrend |
Value: 0 Type: Rate (1/s) Description: Initial trend (fracGrowthRate.initialTrend) |
|---|---|
| fcsth |
Value: 1 Type: Time (s) Description: Forecast horizon |
| tppc |
Value: 1 Type: Time (s) Description: Averaging time for perception of current quantity (i.e., the present condition) |
| thrc |
Value: 1 Type: Time (s) Description: Time horizon for reference condition |
| tpt |
Value: 1 Type: Time (s) Description: Time to perceive the trend (i.e., there is gradual adaptation to a new trend) |
| smoothTrend |
Value: false Type: Boolean Description: = true, if the calculated trend is to be smoothed (fracGrowthRate.smoothTrend) |
Connectors (2)
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y |
Type: RealOutput Description: Information output signal |
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u |
Type: RealInput Description: Current value as basis for trend formulation |
Components (8)
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fractionalGrowth |
Type: Product_2 Description: FractionalGrowthRate times perceptionTime |
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extrapolationFactor |
Type: Add_2 Description: Extrapolaton factor using fractional growth rate and perception time to eliminate perception lage |
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fracGrowthRate |
Type: Trend Description: TREND-formulation is used to calculate a fractional growth rate |
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extrapolPC |
Type: Product_2 Description: Present Condition extrapolated from perceived quantity and the time to perceive it |
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futureValue |
Type: TimeValueOfMoney Description: Future value according to exponential growth model |
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timePPC |
Type: ConstantConverterTime Description: Time to perceive present condition |
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forecastHorizon |
Type: ConstantConverterTime Description: Forecast horizon (T) |
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one |
Type: ConstantConverter Description: Time to perceive present condition |