Yearly Time-Series Wizard

The Yearly Time-Series Wizard is a tool that helps you construct the various time-series expressions supported by WEAP's Data View. These expressions include functions for interpolation, step functions, smooth curves and linear, exponential and logistic projections. (You may also import many data expressions at once from Excel. See Export to Excel, Import from Excel for details.)

To access the wizard, either right-click on the data table or click on the down arrow on the right side of the expression box, and choose Yearly Time-Series Wizard from the menu.

The wizard is divided into three pages, which you step through using the Next () and Previous () buttons.

Page 1: Projection Method

Use this page to select the type of function you want to create. The functions are summarized in graph form on screen as shown below, and are grouped into two main types.

The three functions on the top row allow you to specify data points for various future years, and the function then calculates the values for intervening years:

The interpolation and smooth curve functions are most useful when you expect data to change gradually (for example when modeling the gradual penetration of some common device such as refrigerators or vehicles). The step function is most useful for specifying "lumpy" changes to your system, such as the construction of new transmission links.

The last three functions allow you to specify historic data values (i.e., values before the Current Accounts). The different functions are then used to extrapolate data forward to calculate future values. Extrapolations are based on linear, exponential or logistic least-squares curve fits. Use these functions with care. The onus is on you to ensure that the projections are reasonable, both in terms of how a) well the estimated curve fits the historical data, and b) how policies and other structural factors may change in the future. In other words, be sure to consider how well you can identify past trends, but also if it is reasonable to expect these past trends to continue into the future. WEAP helps you with task a) by providing various statistics describing the curve-fit: the R2 value, the standard error, and the number of observations. If you need to do a more detailed analysis, we suggest you use the data analysis features built-in to Microsoft Excel, and then link your results to your WEAP analysis (see below).

Page 2: Data Source

On page 2, you select the source of the data for the expression. Select whether you want to enter the data directly (i.e., type it in) or whether you want to link to the values in an external Excel spreadsheet.

Page 3: Data Entry

Depending on your choice on page 2, in page 3 you either enter the data used by the function or select an Excel spreadsheet and range from which to extract the data for the selected time-series function.

See also: Data View, Expressions, Examples of Expressions, Export to Excel, Import from Excel, ExpForecast, Interp, LinForecast, LogisticForecast, Smooth, Step