LOGEST


Returns a table of statistics for an exponential curve that best fits a data set.

Syntax:

LOGEST(yvalues, xvalues, allow_const, stats)

yvalues is a single row or column range specifying the y coordinates in a set of data points.
xvalues is a corresponding single row or column range specifying the x coordinates. If xvalues is omitted it defaults to 1, 2, 3, ..., n
If there is more than one set of x variables, xvalues may be a range with corresponding multiple rows or columns.
LOGEST finds an exponential curve  that best fits the data. With more than one set of variables the curve is of the form .
In order to fit the curve, LOGEST uses linear regression (the "least squares" method) based on the equation .
if allow_const is FALSE the constant a is forced to be one; . If omitted, allow_const defaults to TRUE (a value for a is found).


 to  and a are the coeficients for the equation above.
 to  are the standard error values for the ln(b) values;  is the standard error value for the  value.
 is the determination coefficient RSQ;  is the standard error value for the  estimate.
F is the F statistic (F-observed value); df is the number of degrees of freedom.
 is the regression sum of squares;  is the residual sum of squares.


linest1.png



Example:

logest1.png



In the example above, cells A2:B6 contain the x,y values for a set of points. LOGEST(B2:B6,A2:A6,1,1) returns the statistics for a best fit exponential curve through those points.








 
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