Forecast, 256 forecast – Apple iWork '09 User Manual
Page 256
FORECAST
The FORECAST function returns the forecasted y value for a given x based on sample
values using linear regression analysis.
FORECAST(x-num-date-dur, y-values, x-values)
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x-num-date-dur: The x value for which the function should return a forecasted y
value. x-num-date-dur is a number value, a date/time value, or a duration value.
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y-values: The collection containing the y (dependent) values. y-values is a collection
that can contain number, date/time, or duration values. All values must be of the
same type.
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x-values: The collection containing the x (independent) values. x-values is a
collection that can contain number, date/time, or duration values. All values must be
of the same type.
Usage Notes
All arguments must be of the same type.
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The two arrays must be of the same size.
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If, for example, you had data on the driving speed of a vehicle and its fuel efficiency
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at each speed, fuel efficiency would be the dependent variable (y) and driving speed
would be the independent variable (x).
You can use the SLOPE and INTERCEPT functions to find the equation used to
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calculate forecast values.
Example
Given the following table:
=FORECAST(9, A3:F3, A2:F2) returns 19.
Related Topics
For related functions and additional information, see:
“INTERCEPT” on page 262
“Listing of Statistical Functions” on page 225
256
Chapter 10
Statistical Functions