LOGEST - The function returns an array of data that describes an exponential curve that fits the data given in Excel

The following article introduces you to the LOGEST function - one of the functions in the statistical function group is very popular in Excel.

Description: The function returns the array of data describing the exponential curve in accordance with the given data.

- The equation of the curve is:

y = b * m ^ x

or

y = (b * (m1 ^ x1) * (m2 ^ x2) * _)

Syntax: LOGEST (known_y's, [known_x's], [const], [stats])

Inside:

- known_y's : The set of known y values ​​in the relationship y = b * m ^ x, is a required parameter.

+ If known_y's is in a single column or row -> each known_y's column or row is interpreted as a separate variable.

- known_x's: The set of known x values ​​in the relationship y = b * m ^ x, is a required parameter.

+ known_x's may include 1 or more sets of variables.

+ If known_x's is omitted -> it is assumed to be an array of the same size as known_y's

- const: The logical value determining the value of the constant b, is an optional value including the following values:

+ const = True or ignore -> b is calculated normally.

+ const = False or ignore -> b = 1 and m are adjusted such that: y = m ^ x.

- stats: The logical value that determines the return value with additional regression statistics, is an optional value that includes:

+ stats = True  -> returns additional regression statistics.

+ stats = False  -> returns the coefficient m and the constant b .

Attention:

- The more similar the graph to the exponential curve -> the better the calculated straight line is for your data.

- Where there is only 1 independent variable x -> find the value of the intersection y according to the following formula:

+ Crossing Y (b): INDEX (LOGEST (known_y's, known_x's), 2)

- When entering array constants, you must use commas to separate.

- If the values ​​y are outside the values ​​used to define the equation -> the regression equation may be invalid.

For example:

Find the value as described in the data table below:

1. Calculate the value of the LOGEST function with additional regression statistics (corresponding to stats = True).

- In the cell to calculate enter the formula : = LOGEST (D6: D10, C6: C10, TRUE, TRUE)

- Press Enter -> the return value of the function is:

2. Calculate the value of the LOGEST function with stats = False.

- In the cell to calculate enter the formula: = LOGEST (D6: D10, C6: C10, TRUE, FALSE)

- Press Enter -> return value is:

Above are instructions and some specific examples when using the LOGEST function in Excel.

Good luck!