On Aug 28, 6:58*pm, "Mike Middleton"
wrote:

Thanks for the excellent response, Mike. I've been to the site you
gave and used LINEST in that way before to construct a 6th-order
polynomial trendline. It worked great. But...

For predictions, you can use the coefficients from LINEST in worksheet
formulas...

This is pertains to what I was really asking...

What is the excel formula for creating a prediction for Y based on the
coefficients given in the muliple polynomial regression statistics
produced by LINEST()?

For a 3rd order polynomial, I think it is:

y = (m1 * x1^3) + (m2 * x2^2) + (m3 * x3) + b

whe

m1 = coefficient for x1
m2 = coefficent for x2
m3 = coefficient for x3
b = y-intercept

Also, Mike, the formula...

LINEST(y,x^{1,2,3},1,1)

....will produce statistics for a 3rd order polynomial, correct? I can
only get this to work correctly if I have 3 columns of x variables
(e.g., it seems that the order of the polynomial (i.e., 3rd, 4th, 5th,
etc.) must match the number of columns of x variables). But what if I
want to produce a 6th order polynomial for the same 3 columns of x
variables? I receive a #VALUE! error.

I think I have missed some important point over the years with using
LINEST in this way. Thanks for any clarification you can provide.

Cheers,
Joseph