STEM help / Data dialogs

Time series / Straight Line

The Straight Line time-series lets you implement a simple linear growth using a known value and a constant increment. The straight line is defined using a Base value – a defined value of the straight line at a given period – and an Increment (growth value), which specifies the constant increase (or decrease) of the time-series over time (per year by default). Optional parameters are the Base Period, Increment Period and Constrain parameters.

Base

The value of the time series in the Base Period.

Default: 0.0.

Features See Straight Line, Exponential Growth.

Increment

The amount by which a Straight Line time series increases each year or, more generally, each Increment Period. A negative Increment indicates a decreasing quantity.

Default: 0.0.

Features See Straight Line.

Timing

Base Period

Specifies a particular period when the Base value should apply. This can be a year, a quarter, a month, or even a fully-qualified date.

Default: Y0.

Features See Straight Line, Exponential Growth, Floor and Multiplier.

Increment Period

Defines a reference period for the Increment input (which is interpreted as increment per increment period, such as the change per month or per annum). This indicates how the Increment input should then be scaled in proportion to the length of the current period for calculation.

Default: Year.

Features See Straight Line.

Constrain

A choice of whether the calculated value of a straight line time-series may be lower than a non-negative Base value prior to the Base Period if the Increment is positive (or after the Base Period if the Increment is negative). If the Base value is strictly negative, then this choice governs whether, in either case, the output may exceed this Base value and approach zero.

Yes: the output value is constant prior to the Base Period if the Increment is positive (or after the Base Period if the Increment is negative; or vice versa if the Base value is strictly negative). This option provides a simple way to avoids troublesome negative values.

No: the output is not constrained and maintains a consistent Increment either side of the Base Period.

Default: Yes.

Features See Straight Line.

Options

Alignment

Determines what point in the Base Period or Period the Base value or corresponding values is/are associated with.

Default: End for demand-related inputs, but Beginning for tariffs and cost trends.

Features See Using alignment to relate periods, Shorter time periods.

Step (1)

Constrains the dynamics of any time-series input to yield a constant value for quarterly, annual or even indefinite periods.

Default: Day (no constraint is applied: values evolve smoothly).

Features See Using steps to constrain time-series inputs, Shorter time periods.

 

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