Page 432 - Excel for Scientists and Engineers: Numerical Methods

Appendix 4

Some Equations

for Curve Fitting

This appendix describes a number of equation types that can be used for
curve fitting. Some of the equation types can be handled by Excel's Trendline
utility for charts; these cases are noted below.

Multiple Regression. Multiple regression fits data to a model that defines y
as a function of two or more independent x variables. For example, you might
want to fit the yield of a biological fermentation product as a function of
temperature (0, pressure of COZ gas (P) in the fermenter and fermentation time
(t)
y = a.T + b.P +ct + d (A4- 1)
using data from a series of fermentation experiments with different conditions of
temperature, pressure and time.
Since you can't create a chart with three x-axes (e.g., T, P and t), you can't
use Trendline for multiple regression.

Polynomial Regression. Polynomial regression fits data to a power series
such as equation A4-2:
y = a + bx +cx2 + dx3 + ... (A4-2)

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