Documentation/How Tos/Calc: GROWTH function

GROWTH

Fits an exponential curve to a data set, and returns points on that curve.

Syntax:

GROWTH(yvalues; xvalues; new_xvalues; allow_factor)

data is a range or array containing numerical data.

yvalues and xvalues are single row or column ranges specifying points in a set of data.

GROWTH fits an exponential curve of the form y=bm^x through these data points, using the linear regression method.

If allow_factor is FALSE the factor b in this equation is set to 1; if allow_factor is non-zero, TRUE or omitted the factor b is calculated from the data.

GROWTH returns an array of the y values of the exponential curve found, corresponding to the x values in new_xvalues (or if omitted xvalues). It must be entered as an array formula (for example by using Cntrl-Shift-Enter rather than just Enter).

yvalues and xvalues must be the same size. new_xvalues may have a different size.

Example:

=GROWTH(B2:B6; A2:A6; A2:A7)

when entered as an array formula in cell C2, where the x values in A2:A7 are 4, 5, 6, 7, 8, 9 and the y values in B2:B6 are 1.80, 3.20, 6.20, 12.30, 24.50, finds a best fit exponential curve for those points, and in C2:C7 returns y values on that curve for the x values in A2:A7.

This example shows how GROWTH may be used to predict future values (A7,C7).