EXCEL FORECAST.ETS FUNCTION

Forecast in Excel. Based on a sequence of existing values, the Ets function predicts a future value on a timeline using an exponential smoothing technique.

Syntax :

=FORECAST.ETS( target_datevaluestimeline[seasonality][data completion][aggregation] )

Parameters :

  • The function parameters are as follows:

target date –

  • A date/time for which a value should be predicted.
    (Must be after the most recent date/time in the historical timeline.)

values –

  • An array of previously known historical values for which you wish to anticipate the future point.

Timeline –

  • The independent array of dates/times that relate to each value.
    This must meet the following requirements:
    The timeline array must be the same length as the values array; however, the dates/times in the timeline must have a constant step length between them.                                                                        Depending on the value of the [data completeness] option, up to 30% of points may be missing and dealt with.                                                                                                                                                                      The timeline may contain duplicates, whose associated values will be aggregated according to the [aggregation] option.                                                                                                                                             The timeline’s dates and times can be in any sequence.

[seasonality] –

  • An optional input specifying the algorithm to be used to detect seasonality in data.
    If provided, this must be a positive integer between 0 and 8784, corresponding to:
[seasonality]Algorithm
0No seasonality (i.e. use the linear algorithm for the forecast).
1 (or omitted)Automatically calculate the seasonality and use positive, whole numbers for the length of the seasonal pattern.
integer ≥ 2
& ≤ 8784
Use patterns of this length as the seasonality.

[data completion] –

  • An optional input that specifies how the algorithm should handle missing timeline points.
    If provided, the [data completion] parameter can have a value of 0 or 1, which means:
[data completion]Algorithm
0Treat missing points as having the value zero.
1 (or omitted)Calculate the value for missing points to be the average of the neighbouring values.

[aggregation] –

  • An optional parameter that tells the algorithm how to aggregate data with the same timestamp.
    If provided, this can be any integer between 1 and 7, which means:
[aggregation]Aggregation Method
1 (or omitted)Average
2Count
3Counta
4Max
5Median
6Min
7Sum

Step By Step Guide of FORECAST.ETS Function

Example :

The spreadsheet on the right displays a series of monthly earnings from January 2015 to April 2017. The following values are presented in the chart:
Forecast in Excel.
The Ets function may be used to forecast the value of profits in May 2017, as seen below:

=FORECAST.ETS( A30, B2:B29, A2:A29 )

This gives the result 1461.632054.

The target date, May-2017, is stored in the sample spreadsheet’s field A30.
Although the timeline array (stored in the sample spreadsheet’s cells A2:A29) is arranged chronologically, this is not required for the Forecast.
Ets is a function.
The [seasonality], [data completeness], and [aggregation] inputs have been left out of the function, therefore the default values are used.
(For example, [seasonality] = 1, [data completeness] = 1, and [aggregation] = 0).

  • #N/A – Occurs if the lengths of the given values and timeline arrays disagree.
  • #NUM! – Occurs if either: a consistent step size cannot be established in the provided timeline’s dates/times; orThe provided [seasonality] value is not within the permitted range 0 – 8784; the provided [data completeness] value is not equal to 0 or 1;
    The given [aggregate] value is not in the valid range 1 – 7.
  • #VALUE! – Occurs if one or more of the supplied [seasonality], [data completion], or [aggregation] parameters is not a number.

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