# Extracting Coefficients From A Trend Formula

Can anyone please tell me an easy way to transfer or copy the coefficients of a polynomial equation, say 2nd degree, generated by adding a trend line to an "x-y" scatter chart into cells so they can be used to generate other "y" values using the equation. Thanks.

### '=LINEST(known_y's,known_x's,

'=LINEST(known_y's,known_x's,const,stats)

### 3rd order polynomial

Y = aX2 + bX + c

a coefficient : =INDEX(LINEST(NonLinY,NonLinX^{1,2}),1)
b coefficient : =INDEX(LINEST(NonLinY,NonLinX^{1,2}),1,2)
c coefficient : =INDEX(LINEST(NonLinY,NonLinX^{1,2}),1,3)

where NonLinY are the known Y values
NonLinX are the known X values

All functions must be entered as array functions

### Extracting Coefficients

Thanks for your help. I have tried Linest, but it fits a straight line. My problem is with second order polynomial curves. Is there some other technique?

### second order polynomial curves

not easy..
take a look at this:

### LINEST for extracting coefficients

Nick:

Your suggested link worked in a round-about-way. It included a link to Chandoo.org that included an example for deriving coefficients from polynomial functions. I stand corrected. LINEST can be used to accomplish our goal. Thank you for the help!