SOLUTION: I'm stumped. Given an array of known X and Y values, and a list of *new* X values, how can I solve for what the new Y value will be ? A bit more detail: In Excel, I plotted t

SOLUTION: I'm stumped. Given an array of known X and Y values, and a list of new X values, how can I solve for what the new Y value will be ? A bit more detail: In Excel, I plotted t

Question 313163: I'm stumped.
Given an array of known X and Y values, and a list of *new* X values, how can I solve for what the new Y value will be ?
A bit more detail: In Excel, I plotted these known X and Y values by means of a XY Scatter Chart, then asked it to create me a Trend Line, showing me the formula. The formula, for this data, is: y = 14.132x� - 63.03x + 79.647. I need to know how to actually *arrive* at that formula by a more manual means.
Thanks! :)
Answer by Fombitz(32388) (Show Source): You can put this solution on YOUR website!
Check out the link below for the particulars.
You can do this all within an EXCEL spreadsheet.
You're trying to fit to the given sets of data (,).
.
.
.
You need to create a matrix of values.
[X]=
where

.
.
.
Then create another matrix of values,
[Y]=
where

Then you have the coefficients a0,a1, and a2.
[a]=
.
.
.
The matrix equation you need to solve is,
[X][a]=[Y]
[a]=[X]inv[Y]
So find the inverse of [X] and matrix multiply by [Y].
That will provide you the coefficients of the least square fit quadratic, [a].
.
.
.
http://mathworld.wolfram.com/LeastSquaresFittingPolynomial.html
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