Using Time-Series Functions

See also: Analysis View, Expressions, Pasting Arrays of Numbers into LEAP

LEAP supports various time series functions, which let you specify historical data, fill gaps in data using the Interp, Step and Smooth functions and forecast future values using the LinForecast, ExpForecast and LogisticForecast methodologies.  Each of these functions need to be supplied with time-series data, consisting of pairs of year/value data and an optional percentage growth rate parameter, which is applied after the last data year.  This time-series data can be specified in three ways:

  1. As data typed directly into the function.   

    Interp(Year1, Value1, Year2, Value2,... YearN, ValueN, [% Growthrate])

  2. As a reference to data in an MS-Excel spreadsheet.  

    Interp(ExcelFile, ExcelRange, [% Growthrate])

    See also: Specifying Excel File and Range Parameters

  1. As a reference to data in another LEAP branch/variable.  The data in the referenced cell must be specified using the Data function and must consist only of year/value time series pairs.  

    For example, suppose you had the following fuel price data recorded in a branch named Key Assumptions\Price:
    Data(1990, 110 1991, 105, 1992, 108, 1994, 112, 1995, 115, 1996, 109, 1997, 135, 1998, 150)

This data could then be referenced by any timer-series function through a reference to the branch, such as:
Interp(Key\Price)

Use the LEAP Time-series Wizard to simplify entering time-series data and to specify links to Excel data.  When specifying time-series data, years should be in chronological order.  Duplicate years are not allowed, and years must be in the range 1900-2200.