Excel Solver-Polynomial Coefficients Resolved to Zero

You should uncheck the option "Make Unconstrained Variables Non-Negative".

HTH,

Francesco

Is this going to produce a "better" result than using LINEST to return the polynomial fit parameters?

For the cubic polynomial, the formula used is:


=INDEX(LINEST($B$3:$B$13,$A$3:$A$13^{1,2,3}),ROWS(K$1:K1))

copied down for 4 rows. See orange-shaded cells in the 3rd sheet.


You seem to be using an older version of Excel than me. The formulae are almost certainly enclosed within a pair of { }. These are array formulae.

These are a little different from ordinary formulae in that they MUST be confirmed in the FIRST CELL ONLY by pressing CTRL+SHIFT+ENTER to activate the array, not just ENTER. After that, the array can be dragged down as normal, to cover the desired range.

You will know the array is active when you see the curly brackets { } appear around the outside of your formula. If you do not use CTRL+SHIFT+ENTER you will (almost always) get an error message or an incorrect answer. Press F2 on that cell and try again.

Don't type the curly brackets yourself - it won't work...

It's a lot quicker to use the Excel LINEST formula to calculate those parameters, though....

You're welcome.

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It would be very nice if you were to just click the Add Reputation button at the foot of any of the posts of members who helped you reach a solution.

Finally, if that takes care of your original question, please select "Thread Tools" from the menu link above and mark this thread as SOLVED.

It can be adapted for any order of polynomial with a few keystrokes. if you need anything further regarding implementation, just shout.

You're welcome.

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It would be very nice if you were to just click the Add Reputation button at the foot of any of the posts of members who helped you reach a solution.

Finally, if that takes care of your original question, please select "Thread Tools" from the menu link above and mark this thread as SOLVED.