FORECAST ( x , known-ys , known-xs )
Description: Calculates, or predicts, a future value by using existing values. The predicted value is a y-value for a given x-value. The known values are existing x-values and y-values, and the new value is predicted by using linear regression.
Mathematical Formula:
FORECAST=a+bx, where:
and:
and where x and y are the sample means AVERAGE(known-xs) and AVERAGE(known-ys).
Arguments:
|
Name |
Type |
Description |
|
number |
The data point for which a value is to be predicted. | |
|
known-xs |
array, reference |
The independent data. |
|
known-ys |
array, reference |
The dependent data. |
Return Type and Value: number – The future value.
However, if
• known-xs and known-ys are empty or contain a different number of data points, the return value is unspecified.
• The variance of known-xs equals zero, the return value is unspecified.
[Example:
FORECAST(30,{6,7,9,15,21},{20,28,31,38,40}) results in 10.60725309
end example]