Forecasting - Change

The forecasts can be changed using the Change menu item. We show below two versions of a moving average forecast. The first has all data rows full. To add more data we choose the Add Periods option from the dialog and specify that 5 periods are to be added. The original and changed forecasts are shown below.

The effect of the change is to add five more data periods to the bottom of the table. The moving averages are computed for the new rows, but are not relevant until data is added.

Move up Time

 A second change that might be useful is to move up the data in time. Here we choose the Move up Time option and select 15 periods for the time interval. The original and new forecasts are shown below. The entries in the Periods column are shifted by 15 and the data is shifted correspondingly.

Simulate Data

 This option simulates the entries in the data columns of an existing forecast. When the forecast has been generated with the Simulate command, new random numbers are used to seed the random numbers. For other forecasts, the data columns are simply replaced with newly simulated values.

 Extra data columns are added to the left of the forecasted data. They are handy for storing information associated with the data, such as the date or transaction volume for equity stocks. The change dialog allows the addition of one or more columns as illustrate below.

 Extra results columns are added to the right of the forecasts. They are used to make additional computations related to the forecasts or data. In the example we have added a single column to compute the cumulative values of column F. We have added a title and copied the mean and standard deviation functions into Cells G4 and G5. The initial cumulative value, 0, is placed in G18. Into cell G19, we have placed the formula =IF(F19="***","***",F19+G18) The formula places *** in a cell when the F19 + G18 would return an error, and otherwise shows the sum in the cell. It is only necessary to place the formula in G19, in period 1, because we will use the change command Fill Results to create the remainder of the formulas for this column.

Fill Results

 Using this option of the Change dialog, fills the extra results columns with the contents of period 1. In this case period 1 of column G has a formula, so the fill results option fills the remainder of column G with this formula. The option is very useful when several extra columns are used and the number of periods is large.

Operations Management / Industrial Engineering
Internet
by Paul A. Jensen